<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://www.kratosdefense.com/role/Acquisition" xlink:href="ktos-20191229.xsd#Acquisition" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/AcquisitionAcquisitionTables" xlink:href="ktos-20191229.xsd#AcquisitionAcquisitionTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/AcquisitionAssetsAcquiredAndLiabilitiesAssumedDetails" xlink:href="ktos-20191229.xsd#AcquisitionAssetsAcquiredAndLiabilitiesAssumedDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/AcquisitionConsiderationPaidDetails" xlink:href="ktos-20191229.xsd#AcquisitionConsiderationPaidDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/AcquisitionNarrativeDetails" xlink:href="ktos-20191229.xsd#AcquisitionNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/AcquisitionProFormaFinancialInformationDetails" xlink:href="ktos-20191229.xsd#AcquisitionProFormaFinancialInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/BalanceSheetDetails" xlink:href="ktos-20191229.xsd#BalanceSheetDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/BalanceSheetDetailsAccountsReceivableAndInventoryDetails" xlink:href="ktos-20191229.xsd#BalanceSheetDetailsAccountsReceivableAndInventoryDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/BalanceSheetDetailsPropertyPlantAndEquipmentDetails" xlink:href="ktos-20191229.xsd#BalanceSheetDetailsPropertyPlantAndEquipmentDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/BalanceSheetDetailsTables" xlink:href="ktos-20191229.xsd#BalanceSheetDetailsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/CommitmentsAndContingencies" xlink:href="ktos-20191229.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/ConsolidatedBalanceSheets" xlink:href="ktos-20191229.xsd#ConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:href="ktos-20191229.xsd#ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/ConsolidatedStatementsOfCashFlows" xlink:href="ktos-20191229.xsd#ConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/ConsolidatedStatementsOfComprehensiveIncomeLoss" xlink:href="ktos-20191229.xsd#ConsolidatedStatementsOfComprehensiveIncomeLoss" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/ConsolidatedStatementsOfOperations" xlink:href="ktos-20191229.xsd#ConsolidatedStatementsOfOperations" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/ConsolidatedStatementsOfOperationsParenthetical" xlink:href="ktos-20191229.xsd#ConsolidatedStatementsOfOperationsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/ConsolidatedStatementsOfStockholdersEquity" xlink:href="ktos-20191229.xsd#ConsolidatedStatementsOfStockholdersEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/CoverPage" xlink:href="ktos-20191229.xsd#CoverPage" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/Debt" xlink:href="ktos-20191229.xsd#Debt" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DebtCreditAndSecurityAgreementDetails" xlink:href="ktos-20191229.xsd#DebtCreditAndSecurityAgreementDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DebtFairValueOfLongTermDebtDetails" xlink:href="ktos-20191229.xsd#DebtFairValueOfLongTermDebtDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DebtIssuanceOf65SeniorSecuredNotesDue2025Details" xlink:href="ktos-20191229.xsd#DebtIssuanceOf65SeniorSecuredNotesDue2025Details" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DebtTables" xlink:href="ktos-20191229.xsd#DebtTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DiscontinuedOperations" xlink:href="ktos-20191229.xsd#DiscontinuedOperations" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DiscontinuedOperationsDetails" xlink:href="ktos-20191229.xsd#DiscontinuedOperationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DiscontinuedOperationsResultsOfDiscontinuedOperationsDetails" xlink:href="ktos-20191229.xsd#DiscontinuedOperationsResultsOfDiscontinuedOperationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DiscontinuedOperationsSummaryOfAssetsAndLiabilitiesOfDiscontinuedOperationsDetails" xlink:href="ktos-20191229.xsd#DiscontinuedOperationsSummaryOfAssetsAndLiabilitiesOfDiscontinuedOperationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DiscontinuedOperationsTables" xlink:href="ktos-20191229.xsd#DiscontinuedOperationsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/FairValueMeasurement" xlink:href="ktos-20191229.xsd#FairValueMeasurement" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/GoodwillAndOtherIntangibleAssets" xlink:href="ktos-20191229.xsd#GoodwillAndOtherIntangibleAssets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/GoodwillAndOtherIntangibleAssetsGoodwillDetails" xlink:href="ktos-20191229.xsd#GoodwillAndOtherIntangibleAssetsGoodwillDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/GoodwillAndOtherIntangibleAssetsIntangibleAssetAmortizationDetails" xlink:href="ktos-20191229.xsd#GoodwillAndOtherIntangibleAssetsIntangibleAssetAmortizationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/GoodwillAndOtherIntangibleAssetsPurchasedIntangibleAssetsDetails" xlink:href="ktos-20191229.xsd#GoodwillAndOtherIntangibleAssetsPurchasedIntangibleAssetsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/GoodwillAndOtherIntangibleAssetsTables" xlink:href="ktos-20191229.xsd#GoodwillAndOtherIntangibleAssetsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxes" xlink:href="ktos-20191229.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxesComponentsOfIncomeTaxesDetails" xlink:href="ktos-20191229.xsd#IncomeTaxesComponentsOfIncomeTaxesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxesDeferredTaxesDetails" xlink:href="ktos-20191229.xsd#IncomeTaxesDeferredTaxesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxesNarrativeDetails" xlink:href="ktos-20191229.xsd#IncomeTaxesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxesReconciliationOfIncomeTaxProvisionDetails" xlink:href="ktos-20191229.xsd#IncomeTaxesReconciliationOfIncomeTaxProvisionDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxesTables" xlink:href="ktos-20191229.xsd#IncomeTaxesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails" xlink:href="ktos-20191229.xsd#IncomeTaxesUnrecognizedTaxBenefitsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/Leases" xlink:href="ktos-20191229.xsd#Leases" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesAdditionalInformationDetails" xlink:href="ktos-20191229.xsd#LeasesAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesCashPaidDetails" xlink:href="ktos-20191229.xsd#LeasesCashPaidDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesLeaseExpenseDetails" xlink:href="ktos-20191229.xsd#LeasesLeaseExpenseDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesLeasesTables" xlink:href="ktos-20191229.xsd#LeasesLeasesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesMaturitiesOfOperatingAndFinancingLeaseLiabilitiesDetails" xlink:href="ktos-20191229.xsd#LeasesMaturitiesOfOperatingAndFinancingLeaseLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesOperatingLeaseUnderAsc840Details" xlink:href="ktos-20191229.xsd#LeasesOperatingLeaseUnderAsc840Details" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesSupplementalBalanceSheetDetails" xlink:href="ktos-20191229.xsd#LeasesSupplementalBalanceSheetDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesWeightedAverageDetails" xlink:href="ktos-20191229.xsd#LeasesWeightedAverageDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/NetIncomeLossPerCommonShare" xlink:href="ktos-20191229.xsd#NetIncomeLossPerCommonShare" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/NetIncomeLossPerCommonShareAntidilutiveSecuritiesDetails" xlink:href="ktos-20191229.xsd#NetIncomeLossPerCommonShareAntidilutiveSecuritiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/NetIncomeLossPerCommonShareTables" xlink:href="ktos-20191229.xsd#NetIncomeLossPerCommonShareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPolicies" xlink:href="ktos-20191229.xsd#OrganizationAndSummaryOfSignificantAccountingPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesContractAssetsAndLiabilitiesDetails" xlink:href="ktos-20191229.xsd#OrganizationAndSummaryOfSignificantAccountingPoliciesContractAssetsAndLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesDetails" xlink:href="ktos-20191229.xsd#OrganizationAndSummaryOfSignificantAccountingPoliciesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesDisaggregationOfRevenueDetails" xlink:href="ktos-20191229.xsd#OrganizationAndSummaryOfSignificantAccountingPoliciesDisaggregationOfRevenueDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesPolicies" xlink:href="ktos-20191229.xsd#OrganizationAndSummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesRemainingPerformanceObligationsDetails" xlink:href="ktos-20191229.xsd#OrganizationAndSummaryOfSignificantAccountingPoliciesRemainingPerformanceObligationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesRevenueRecognitionNarrativeDetails" xlink:href="ktos-20191229.xsd#OrganizationAndSummaryOfSignificantAccountingPoliciesRevenueRecognitionNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesTables" xlink:href="ktos-20191229.xsd#OrganizationAndSummaryOfSignificantAccountingPoliciesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/QuarterlyFinancialDataUnaudited" xlink:href="ktos-20191229.xsd#QuarterlyFinancialDataUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/QuarterlyFinancialDataUnauditedSummarizedQuarterlyFinancialInformationDetails" xlink:href="ktos-20191229.xsd#QuarterlyFinancialDataUnauditedSummarizedQuarterlyFinancialInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/QuarterlyFinancialDataUnauditedTables" xlink:href="ktos-20191229.xsd#QuarterlyFinancialDataUnauditedTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RedeemableNoncontrollingInterest" xlink:href="ktos-20191229.xsd#RedeemableNoncontrollingInterest" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RetirementPlans" xlink:href="ktos-20191229.xsd#RetirementPlans" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RetirementPlansDetails" xlink:href="ktos-20191229.xsd#RetirementPlansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SegmentInformation" xlink:href="ktos-20191229.xsd#SegmentInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SegmentInformationNarrativeDetails" xlink:href="ktos-20191229.xsd#SegmentInformationNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SegmentInformationRevenuesOperatingIncomeLossAndAssetsByReportableSegmentsDetails" xlink:href="ktos-20191229.xsd#SegmentInformationRevenuesOperatingIncomeLossAndAssetsByReportableSegmentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SegmentInformationTables" xlink:href="ktos-20191229.xsd#SegmentInformationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SignificantCustomers" xlink:href="ktos-20191229.xsd#SignificantCustomers" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SignificantCustomersDetails" xlink:href="ktos-20191229.xsd#SignificantCustomersDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/StockholdersEquity" xlink:href="ktos-20191229.xsd#StockholdersEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/StockholdersEquityCommonStockDetails" xlink:href="ktos-20191229.xsd#StockholdersEquityCommonStockDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/StockholdersEquityEmployeeStockPurchasePlanDetails" xlink:href="ktos-20191229.xsd#StockholdersEquityEmployeeStockPurchasePlanDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/StockholdersEquityGrantsAndExercisesUnderOptionPlansDetails" xlink:href="ktos-20191229.xsd#StockholdersEquityGrantsAndExercisesUnderOptionPlansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/StockholdersEquityRestrictedStockUnitActivityDetails" xlink:href="ktos-20191229.xsd#StockholdersEquityRestrictedStockUnitActivityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/StockholdersEquityStockOptionPlansAndRestrictedStockUnitsPlansDetails" xlink:href="ktos-20191229.xsd#StockholdersEquityStockOptionPlansAndRestrictedStockUnitsPlansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/StockholdersEquityStockOptionValuationAssumptionsDetails" xlink:href="ktos-20191229.xsd#StockholdersEquityStockOptionValuationAssumptionsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/StockholdersEquityStockOptionsRollForwardDetails" xlink:href="ktos-20191229.xsd#StockholdersEquityStockOptionsRollForwardDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/StockholdersEquityStockholdersEquityTables" xlink:href="ktos-20191229.xsd#StockholdersEquityStockholdersEquityTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SubsequentEvents" xlink:href="ktos-20191229.xsd#SubsequentEvents" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SubsequentEventsDetails" xlink:href="ktos-20191229.xsd#SubsequentEventsDetails" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/Acquisition" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/AcquisitionAcquisitionTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/AcquisitionAssetsAcquiredAndLiabilitiesAssumedDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_0F0E61A4EA8EC308761B77CD21A00B35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_0F0E61A4EA8EC308761B77CD21A00B35" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_5E44773D9B7292B53C8B77CD21A0C0D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_0F0E61A4EA8EC308761B77CD21A00B35" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_5E44773D9B7292B53C8B77CD21A0C0D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6F8E3D0A0298F9CDB7EC77CD21A02422_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5E44773D9B7292B53C8B77CD21A0C0D3" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6F8E3D0A0298F9CDB7EC77CD21A02422_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6F8E3D0A0298F9CDB7EC77CD21A02422" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5E44773D9B7292B53C8B77CD21A0C0D3" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6F8E3D0A0298F9CDB7EC77CD21A02422" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_FTTIncMember" xlink:label="loc_ktos_FTTIncMember_ACB57B52D32A9C4C5A7677CD21A1439E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6F8E3D0A0298F9CDB7EC77CD21A02422" xlink:to="loc_ktos_FTTIncMember_ACB57B52D32A9C4C5A7677CD21A1439E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_1A96632930DD5F8EFEA277CD21A24C74" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_1A96632930DD5F8EFEA277CD21A24C74" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsUnbilledReceivables" xlink:label="loc_ktos_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsUnbilledReceivables_04AE74A8DE1CA97B8E8277CD21A27B68" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_ktos_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsUnbilledReceivables_04AE74A8DE1CA97B8E8277CD21A27B68" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_9F6CA8B55E1103BC9C7677CD21A24F7D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_9F6CA8B55E1103BC9C7677CD21A24F7D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_7CA112038F1659E65F4F77CD21A2A5E7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_7CA112038F1659E65F4F77CD21A2A5E7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_7D3740901959857E7C4377CD21A37EDF" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_7D3740901959857E7C4377CD21A37EDF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_780CB1F287D4E76405CE77CD21A37757" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_780CB1F287D4E76405CE77CD21A37757" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_0D6B9204E79EDC412B0077CD21A35CBE" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_Goodwill_0D6B9204E79EDC412B0077CD21A35CBE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_CCF9836A265D1310121F77CD21A394D8" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_CCF9836A265D1310121F77CD21A394D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_5B831DCCB01528D42EEB77CD21A44260" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_5B831DCCB01528D42EEB77CD21A44260" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_26C2DE31928E5BDFAFE777CD21A47BC7" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_26C2DE31928E5BDFAFE777CD21A47BC7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue_97CD9F3CA349E82D08E877CD21A4E376" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue_97CD9F3CA349E82D08E877CD21A4E376" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest_EA4EE1EC46B8FDC1615F77CD21A4DE4A" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2E5C9490EC2D9B522F4977CD21A15372" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest_EA4EE1EC46B8FDC1615F77CD21A4DE4A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/AcquisitionConsiderationPaidDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_07E3468D834D527B74A577CD21945390" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_A608B577B66DD3D420B277CD21929E44" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_07E3468D834D527B74A577CD21945390" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_A608B577B66DD3D420B277CD21929E44" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_FF66BF9C939CFC39191577CD21935B95" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_A608B577B66DD3D420B277CD21929E44" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_FF66BF9C939CFC39191577CD21935B95" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3B738652E23ACE54FE4377CD2193C33C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_FF66BF9C939CFC39191577CD21935B95" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3B738652E23ACE54FE4377CD2193C33C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3B738652E23ACE54FE4377CD2193C33C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_FF66BF9C939CFC39191577CD21935B95" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3B738652E23ACE54FE4377CD2193C33C" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_FTTIncMember" xlink:label="loc_ktos_FTTIncMember_554FB59743C071C4CC6477CD21930ED2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3B738652E23ACE54FE4377CD2193C33C" xlink:to="loc_ktos_FTTIncMember_554FB59743C071C4CC6477CD21930ED2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_FF6CC96A8270642F5C9877CD2194368A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_07E3468D834D527B74A577CD21945390" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_FF6CC96A8270642F5C9877CD2194368A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_4588D0A663FFDCA4561C77CD21943B6B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_07E3468D834D527B74A577CD21945390" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_4588D0A663FFDCA4561C77CD21943B6B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_BA664AADD207621A05CA77CD2195B947" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_07E3468D834D527B74A577CD21945390" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_BA664AADD207621A05CA77CD2195B947" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_BusinessCombinationConsiderationTransferredGross" xlink:label="loc_ktos_BusinessCombinationConsiderationTransferredGross_2AC0A1D54A83490723F977CD2195B5AD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_07E3468D834D527B74A577CD21945390" xlink:to="loc_ktos_BusinessCombinationConsiderationTransferredGross_2AC0A1D54A83490723F977CD2195B5AD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashAcquiredFromAcquisition" xlink:label="loc_us-gaap_CashAcquiredFromAcquisition_B31AF3BBF45F1875401477CD2195447C" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_07E3468D834D527B74A577CD21945390" xlink:to="loc_us-gaap_CashAcquiredFromAcquisition_B31AF3BBF45F1875401477CD2195447C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_87E86DA2D160B5D186B577CD21952ADE" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_07E3468D834D527B74A577CD21945390" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_87E86DA2D160B5D186B577CD21952ADE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/AcquisitionNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57DA8F5399DE09C9B60A77CD21B0EA83" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57DA8F5399DE09C9B60A77CD21B0EA83" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_2C040A94B534D449737577CD21B04E04" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57DA8F5399DE09C9B60A77CD21B0EA83" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_2C040A94B534D449737577CD21B04E04" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CC86454320771531CF4577CD21B142A6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_2C040A94B534D449737577CD21B04E04" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CC86454320771531CF4577CD21B142A6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CC86454320771531CF4577CD21B142A6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_2C040A94B534D449737577CD21B04E04" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CC86454320771531CF4577CD21B142A6" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_FloridaTurbineTechnologiesInc.Member" xlink:label="loc_ktos_FloridaTurbineTechnologiesInc.Member_DCECEF11D5371926935277CD21B1CD86" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CC86454320771531CF4577CD21B142A6" xlink:to="loc_ktos_FloridaTurbineTechnologiesInc.Member_DCECEF11D5371926935277CD21B1CD86" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_FTTCoreLLCMember" xlink:label="loc_ktos_FTTCoreLLCMember_72FB37E631C7E1CBC05777CD21B11F2A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CC86454320771531CF4577CD21B142A6" xlink:to="loc_ktos_FTTCoreLLCMember_72FB37E631C7E1CBC05777CD21B11F2A" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_FTTIncMember" xlink:label="loc_ktos_FTTIncMember_C72F933BCB2022B95DCB77CD21B1C66E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CC86454320771531CF4577CD21B142A6" xlink:to="loc_ktos_FTTIncMember_C72F933BCB2022B95DCB77CD21B1C66E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_E8BFD87D9B63FD249FA977CD21B28D42" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57DA8F5399DE09C9B60A77CD21B0EA83" xlink:to="loc_us-gaap_StatementClassOfStockAxis_E8BFD87D9B63FD249FA977CD21B28D42" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_7E9EDBE646E3A05A3DCB77CD21B24236_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_E8BFD87D9B63FD249FA977CD21B28D42" xlink:to="loc_us-gaap_ClassOfStockDomain_7E9EDBE646E3A05A3DCB77CD21B24236_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_7E9EDBE646E3A05A3DCB77CD21B24236" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_E8BFD87D9B63FD249FA977CD21B28D42" xlink:to="loc_us-gaap_ClassOfStockDomain_7E9EDBE646E3A05A3DCB77CD21B24236" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_2840B2224ABDC6D1E4FC77CD21B2B9A6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_7E9EDBE646E3A05A3DCB77CD21B24236" xlink:to="loc_us-gaap_CommonStockMember_2840B2224ABDC6D1E4FC77CD21B2B9A6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_62C80A5551B6A218B17377CD21B3A2C6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57DA8F5399DE09C9B60A77CD21B0EA83" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_62C80A5551B6A218B17377CD21B3A2C6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_85DD5FAFD54DA1D0718077CD21B3D9AC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_62C80A5551B6A218B17377CD21B3A2C6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_85DD5FAFD54DA1D0718077CD21B3D9AC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_85DD5FAFD54DA1D0718077CD21B3D9AC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_62C80A5551B6A218B17377CD21B3A2C6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_85DD5FAFD54DA1D0718077CD21B3D9AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CustomerRelationshipsMember" xlink:label="loc_us-gaap_CustomerRelationshipsMember_D0F1BDC037149B54B27D77CD21B39F09" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_85DD5FAFD54DA1D0718077CD21B3D9AC" xlink:to="loc_us-gaap_CustomerRelationshipsMember_D0F1BDC037149B54B27D77CD21B39F09" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InProcessResearchAndDevelopmentMember" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_A443B717E820CB73776277CD21B48073" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_85DD5FAFD54DA1D0718077CD21B3D9AC" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_A443B717E820CB73776277CD21B48073" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_ContractsAndBacklogMember" xlink:label="loc_ktos_ContractsAndBacklogMember_7D99D38705E6BC13172377CD21B42131" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_85DD5FAFD54DA1D0718077CD21B3D9AC" xlink:to="loc_ktos_ContractsAndBacklogMember_7D99D38705E6BC13172377CD21B42131" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TradeNamesMember" xlink:label="loc_us-gaap_TradeNamesMember_205F381439FB673F292677CD21B4AF87" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_85DD5FAFD54DA1D0718077CD21B3D9AC" xlink:to="loc_us-gaap_TradeNamesMember_205F381439FB673F292677CD21B4AF87" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_5C36B2E49D814A19DE0F77E7399B598E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57DA8F5399DE09C9B60A77CD21B0EA83" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_5C36B2E49D814A19DE0F77E7399B598E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_C077A97B444BFC8A288E77E7750D5438_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_5C36B2E49D814A19DE0F77E7399B598E" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_C077A97B444BFC8A288E77E7750D5438_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_C077A97B444BFC8A288E77E7750D5438" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_5C36B2E49D814A19DE0F77E7399B598E" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_C077A97B444BFC8A288E77E7750D5438" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputDiscountRateMember" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_9D519B86C65DA34DE37C77E7F8D4EABB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_C077A97B444BFC8A288E77E7750D5438" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_9D519B86C65DA34DE37C77E7F8D4EABB" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_MeasurementInputRoyaltyRateMember" xlink:label="loc_ktos_MeasurementInputRoyaltyRateMember_96FF5F8FC495DD81C60177ED16BDC77B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_C077A97B444BFC8A288E77E7750D5438" xlink:to="loc_ktos_MeasurementInputRoyaltyRateMember_96FF5F8FC495DD81C60177ED16BDC77B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationTechniqueAxis" xlink:label="loc_us-gaap_ValuationTechniqueAxis_CC515C19323BF838F90677E8A4EF3A89" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57DA8F5399DE09C9B60A77CD21B0EA83" xlink:to="loc_us-gaap_ValuationTechniqueAxis_CC515C19323BF838F90677E8A4EF3A89" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationTechniqueDomain" xlink:label="loc_us-gaap_ValuationTechniqueDomain_6D088D288005E4EB1C2977E8E233B5E4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationTechniqueAxis_CC515C19323BF838F90677E8A4EF3A89" xlink:to="loc_us-gaap_ValuationTechniqueDomain_6D088D288005E4EB1C2977E8E233B5E4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationTechniqueDomain" xlink:label="loc_us-gaap_ValuationTechniqueDomain_6D088D288005E4EB1C2977E8E233B5E4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationTechniqueAxis_CC515C19323BF838F90677E8A4EF3A89" xlink:to="loc_us-gaap_ValuationTechniqueDomain_6D088D288005E4EB1C2977E8E233B5E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeApproachValuationTechniqueMember" xlink:label="loc_us-gaap_IncomeApproachValuationTechniqueMember_9DD02C57184CB698D33277E91CCE87C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_6D088D288005E4EB1C2977E8E233B5E4" xlink:to="loc_us-gaap_IncomeApproachValuationTechniqueMember_9DD02C57184CB698D33277E91CCE87C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_EEB13766A6D7A8B3D22F77E60F29EBF0" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57DA8F5399DE09C9B60A77CD21B0EA83" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_EEB13766A6D7A8B3D22F77E60F29EBF0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5B0C87F82A98DA9DDEDE77E650102C65_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_EEB13766A6D7A8B3D22F77E60F29EBF0" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5B0C87F82A98DA9DDEDE77E650102C65_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5B0C87F82A98DA9DDEDE77E650102C65" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_EEB13766A6D7A8B3D22F77E60F29EBF0" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5B0C87F82A98DA9DDEDE77E650102C65" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_15AD3E2849872C52DBDF77E68440F8E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5B0C87F82A98DA9DDEDE77E650102C65" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_15AD3E2849872C52DBDF77E68440F8E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_295D4555818138C8273F77CD21B451E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_295D4555818138C8273F77CD21B451E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_F78CF30672D9D5A6723677CD21B53ECF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_F78CF30672D9D5A6723677CD21B53ECF" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_PaymentstoAcquireBusinessesGrossIncludingAmountsToBePaid" xlink:label="loc_ktos_PaymentstoAcquireBusinessesGrossIncludingAmountsToBePaid_F2DA8E0C2A6D509094AA77CD21B5F48C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_ktos_PaymentstoAcquireBusinessesGrossIncludingAmountsToBePaid_F2DA8E0C2A6D509094AA77CD21B5F48C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_3F13D278E111713D520877CD21B50281" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_3F13D278E111713D520877CD21B50281" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_PaymentstoAcquireBusinessesAmountToBePaid" xlink:label="loc_ktos_PaymentstoAcquireBusinessesAmountToBePaid_A317ADF3ACAEEAFC1AC477CD21B510A2" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_ktos_PaymentstoAcquireBusinessesAmountToBePaid_A317ADF3ACAEEAFC1AC477CD21B510A2" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_PaymentstoAcquireBusinessesPaymentPeriod" xlink:label="loc_ktos_PaymentstoAcquireBusinessesPaymentPeriod_5272998FCD8C1611D37577DBD332E541" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_ktos_PaymentstoAcquireBusinessesPaymentPeriod_5272998FCD8C1611D37577DBD332E541" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued" xlink:label="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_1507E32B229ABBC8505777CD21B6AFFD" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_1507E32B229ABBC8505777CD21B6AFFD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned" xlink:label="loc_us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned_7410A964B6F42BA7F4E577CD21B6750B" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned_7410A964B6F42BA7F4E577CD21B6750B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_10BE3D7D6400C4DB232077CD21B6FE23" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_10BE3D7D6400C4DB232077CD21B6FE23" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinitelivedIntangibleAssetsAcquired1" xlink:label="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_C2FB8ECE90CDCD5B6CEB77CD21B62928" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_C2FB8ECE90CDCD5B6CEB77CD21B62928" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_3A2CFD43FD927DB9A73177CD21B6BBEB" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_3A2CFD43FD927DB9A73177CD21B6BBEB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredTaxLiabilities" xlink:label="loc_us-gaap_DeferredTaxLiabilities_C3D8374518C7D21CA8D877CD21B74665" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_DeferredTaxLiabilities_C3D8374518C7D21CA8D877CD21B74665" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_D734D98BE06C1454E8D977E99155DBD8" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_D734D98BE06C1454E8D977E99155DBD8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_5A9A28631B4D2B4F32EB77CD21B77B6E" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_5A9A28631B4D2B4F32EB77CD21B77B6E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_25A10115D4D04779757177CD21B71F20" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_25A10115D4D04779757177CD21B71F20" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_8EE94206685036E7FD2A77CD21B73A12" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_A3639E72A8E65236110777CD21B446F9" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_8EE94206685036E7FD2A77CD21B73A12" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/AcquisitionProFormaFinancialInformationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_3C87C1D0FBD558837B8377CD2189B6DA" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_DE3A4C079923776AF00277CD2187BA78" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3C87C1D0FBD558837B8377CD2189B6DA" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_DE3A4C079923776AF00277CD2187BA78" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_7C9BFCCDC574B366C42077CD2187F3A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_DE3A4C079923776AF00277CD2187BA78" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_7C9BFCCDC574B366C42077CD2187F3A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_F26C267615FD6ED165AA77CD21882B69_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_7C9BFCCDC574B366C42077CD2187F3A4" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_F26C267615FD6ED165AA77CD21882B69_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_F26C267615FD6ED165AA77CD21882B69" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_7C9BFCCDC574B366C42077CD2187F3A4" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_F26C267615FD6ED165AA77CD21882B69" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_FTTIncMember" xlink:label="loc_ktos_FTTIncMember_6605391E8BEC1D82263377CD21883195" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_F26C267615FD6ED165AA77CD21882B69" xlink:to="loc_ktos_FTTIncMember_6605391E8BEC1D82263377CD21883195" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionsProFormaRevenue" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_7DAE8154A1D0FAAFAB3077CD218975DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3C87C1D0FBD558837B8377CD2189B6DA" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_7DAE8154A1D0FAAFAB3077CD218975DB" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_BusinessAcquisitionProFormaIncomeLossfromContinuingOperationsBeforeTax" xlink:label="loc_ktos_BusinessAcquisitionProFormaIncomeLossfromContinuingOperationsBeforeTax_0C90BB82CCD7B8E9D62977CD2189BD4F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3C87C1D0FBD558837B8377CD2189B6DA" xlink:to="loc_ktos_BusinessAcquisitionProFormaIncomeLossfromContinuingOperationsBeforeTax_0C90BB82CCD7B8E9D62977CD2189BD4F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_B2F493E881CEE9C4C64C77CD2189C4A0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3C87C1D0FBD558837B8377CD2189B6DA" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_B2F493E881CEE9C4C64C77CD2189C4A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_28D324832A7F80F7773177CD218AD87A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3C87C1D0FBD558837B8377CD2189B6DA" xlink:to="loc_us-gaap_NetIncomeLoss_28D324832A7F80F7773177CD218AD87A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic_5FF3299AB9E9E3A0256177CD218AC040" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3C87C1D0FBD558837B8377CD2189B6DA" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic_5FF3299AB9E9E3A0256177CD218AC040" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted_FEB96DF907213C5635AB77CD218A055A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3C87C1D0FBD558837B8377CD2189B6DA" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted_FEB96DF907213C5635AB77CD218A055A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/BalanceSheetDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/BalanceSheetDetailsAccountsReceivableAndInventoryDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_41A4D78603FD5C442964640D3B0C6283" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_3675AE8979494B43CE79640D3B0A0C63" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_41A4D78603FD5C442964640D3B0C6283" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_3675AE8979494B43CE79640D3B0A0C63" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis_0C28F43CB275057154C8640D3B0A7F82" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_3675AE8979494B43CE79640D3B0A0C63" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis_0C28F43CB275057154C8640D3B0A7F82" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LegalEntityTypeOfCounterpartyDomain" xlink:label="loc_us-gaap_LegalEntityTypeOfCounterpartyDomain_010E2FE237269FE71B0C640D3B0B7261_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis_0C28F43CB275057154C8640D3B0A7F82" xlink:to="loc_us-gaap_LegalEntityTypeOfCounterpartyDomain_010E2FE237269FE71B0C640D3B0B7261_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LegalEntityTypeOfCounterpartyDomain" xlink:label="loc_us-gaap_LegalEntityTypeOfCounterpartyDomain_010E2FE237269FE71B0C640D3B0B7261" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis_0C28F43CB275057154C8640D3B0A7F82" xlink:to="loc_us-gaap_LegalEntityTypeOfCounterpartyDomain_010E2FE237269FE71B0C640D3B0B7261" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GovernmentMember" xlink:label="loc_us-gaap_GovernmentMember_F469957DCB8F4DEBDFC2640D3B0B9FFF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LegalEntityTypeOfCounterpartyDomain_010E2FE237269FE71B0C640D3B0B7261" xlink:to="loc_us-gaap_GovernmentMember_F469957DCB8F4DEBDFC2640D3B0B9FFF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis_586B9EA478D6E73A006B640D3B0B737E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_3675AE8979494B43CE79640D3B0A0C63" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis_586B9EA478D6E73A006B640D3B0B737E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivablesBillingStatusDomain" xlink:label="loc_us-gaap_ReceivablesBillingStatusDomain_C06B6C0A62666908FD04640D3B0B10BC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis_586B9EA478D6E73A006B640D3B0B737E" xlink:to="loc_us-gaap_ReceivablesBillingStatusDomain_C06B6C0A62666908FD04640D3B0B10BC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivablesBillingStatusDomain" xlink:label="loc_us-gaap_ReceivablesBillingStatusDomain_C06B6C0A62666908FD04640D3B0B10BC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis_586B9EA478D6E73A006B640D3B0B737E" xlink:to="loc_us-gaap_ReceivablesBillingStatusDomain_C06B6C0A62666908FD04640D3B0B10BC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BilledRevenuesMember" xlink:label="loc_us-gaap_BilledRevenuesMember_4D67BFE049EB9057D607640D3B0CF9E6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivablesBillingStatusDomain_C06B6C0A62666908FD04640D3B0B10BC" xlink:to="loc_us-gaap_BilledRevenuesMember_4D67BFE049EB9057D607640D3B0CF9E6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnbilledRevenuesMember" xlink:label="loc_us-gaap_UnbilledRevenuesMember_F5B290E59096BD9B6B2F640D3B0CFDCE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivablesBillingStatusDomain_C06B6C0A62666908FD04640D3B0B10BC" xlink:to="loc_us-gaap_UnbilledRevenuesMember_F5B290E59096BD9B6B2F640D3B0CFDCE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsReceivableGrossCurrent" xlink:label="loc_us-gaap_AccountsReceivableGrossCurrent_826659F33E4C808346B6640D3B0CA22F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_41A4D78603FD5C442964640D3B0C6283" xlink:to="loc_us-gaap_AccountsReceivableGrossCurrent_826659F33E4C808346B6640D3B0CA22F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_A5889EBA542DCBF5337B640D3B0D8619" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_41A4D78603FD5C442964640D3B0C6283" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_A5889EBA542DCBF5337B640D3B0D8619" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsReceivableNetNoncurrent" xlink:label="loc_us-gaap_AccountsReceivableNetNoncurrent_27E9F98E3CC5AB28AA7D640D3B0DD6B5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_41A4D78603FD5C442964640D3B0C6283" xlink:to="loc_us-gaap_AccountsReceivableNetNoncurrent_27E9F98E3CC5AB28AA7D640D3B0DD6B5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsReceivableNet" xlink:label="loc_us-gaap_AccountsReceivableNet_D5ED69D52CD1B72B786C640D3B0D6E28" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_41A4D78603FD5C442964640D3B0C6283" xlink:to="loc_us-gaap_AccountsReceivableNet_D5ED69D52CD1B72B786C640D3B0D6E28" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/BalanceSheetDetailsPropertyPlantAndEquipmentDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_5F5A8D538E632D0D7836640D3B03FF37" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_768E2FFC9600F3011075640D3B01AE42" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_5F5A8D538E632D0D7836640D3B03FF37" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_768E2FFC9600F3011075640D3B01AE42" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4EC2A2DA0BD4F6497CC7640D3B014012" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_768E2FFC9600F3011075640D3B01AE42" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4EC2A2DA0BD4F6497CC7640D3B014012" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_F072CD3225A81B98F365640D3B01A28A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4EC2A2DA0BD4F6497CC7640D3B014012" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_F072CD3225A81B98F365640D3B01A28A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_F072CD3225A81B98F365640D3B01A28A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4EC2A2DA0BD4F6497CC7640D3B014012" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_F072CD3225A81B98F365640D3B01A28A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LandAndBuildingMember" xlink:label="loc_us-gaap_LandAndBuildingMember_7C44EC86B0C3C3497E6C640D3B01C82A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_F072CD3225A81B98F365640D3B01A28A" xlink:to="loc_us-gaap_LandAndBuildingMember_7C44EC86B0C3C3497E6C640D3B01C82A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComputerEquipmentMember" xlink:label="loc_us-gaap_ComputerEquipmentMember_7E332003FE4E97E2BB07640D3B02EAF6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_F072CD3225A81B98F365640D3B01A28A" xlink:to="loc_us-gaap_ComputerEquipmentMember_7E332003FE4E97E2BB07640D3B02EAF6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherMachineryAndEquipmentMember" xlink:label="loc_us-gaap_OtherMachineryAndEquipmentMember_FA284505D12AEA41EFB3640D3B029A61" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_F072CD3225A81B98F365640D3B01A28A" xlink:to="loc_us-gaap_OtherMachineryAndEquipmentMember_FA284505D12AEA41EFB3640D3B029A61" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OfficeEquipmentMember" xlink:label="loc_us-gaap_OfficeEquipmentMember_B12CC42952259ACE0CB0640D3B02D734" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_F072CD3225A81B98F365640D3B01A28A" xlink:to="loc_us-gaap_OfficeEquipmentMember_B12CC42952259ACE0CB0640D3B02D734" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_1293767BDBCFC1FEAEF0640D3B025B57" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_F072CD3225A81B98F365640D3B01A28A" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_1293767BDBCFC1FEAEF0640D3B025B57" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionInProgressMember" xlink:label="loc_us-gaap_ConstructionInProgressMember_06E531544DC8438FB050640D3B02A6CF" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_F072CD3225A81B98F365640D3B01A28A" xlink:to="loc_us-gaap_ConstructionInProgressMember_06E531544DC8438FB050640D3B02A6CF" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_FinanceLeaseRightofUseAssetbeforeAccumulatedAmortization" xlink:label="loc_ktos_FinanceLeaseRightofUseAssetbeforeAccumulatedAmortization_8C346A3AB80BA41B1DFF641C02A623DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_5F5A8D538E632D0D7836640D3B03FF37" xlink:to="loc_ktos_FinanceLeaseRightofUseAssetbeforeAccumulatedAmortization_8C346A3AB80BA41B1DFF641C02A623DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_20AFDD3B3B0D95053D42640D3B033AE1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_5F5A8D538E632D0D7836640D3B03FF37" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_20AFDD3B3B0D95053D42640D3B033AE1" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_PropertyPlantandEquipmentandFinanceLeaseRightofUseAssetbeforeAccumulatedDepreciationandAmortization" xlink:label="loc_ktos_PropertyPlantandEquipmentandFinanceLeaseRightofUseAssetbeforeAccumulatedDepreciationandAmortization_8CA08F58C1BEA9437298641D42F7649A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_5F5A8D538E632D0D7836640D3B03FF37" xlink:to="loc_ktos_PropertyPlantandEquipmentandFinanceLeaseRightofUseAssetbeforeAccumulatedDepreciationandAmortization_8CA08F58C1BEA9437298641D42F7649A" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_PropertyPlantandEquipmentandFinanceLeaseRightofUseAssetAccumulatedDepreciationandAmortization" xlink:label="loc_ktos_PropertyPlantandEquipmentandFinanceLeaseRightofUseAssetAccumulatedDepreciationandAmortization_FBEA91A28DB0AC8FEEF7641DD09D63DC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_5F5A8D538E632D0D7836640D3B03FF37" xlink:to="loc_ktos_PropertyPlantandEquipmentandFinanceLeaseRightofUseAssetAccumulatedDepreciationandAmortization_FBEA91A28DB0AC8FEEF7641DD09D63DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_674849F52CE85151670F640D3B037642" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_5F5A8D538E632D0D7836640D3B03FF37" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_674849F52CE85151670F640D3B037642" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_PropertyPlantandEquipmentandFinanceLeaseRightofUseAssetafterAccumulatedDepreciationandAmortization" xlink:label="loc_ktos_PropertyPlantandEquipmentandFinanceLeaseRightofUseAssetafterAccumulatedDepreciationandAmortization_1053C62E7C6068496955641E78032E24" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_5F5A8D538E632D0D7836640D3B03FF37" xlink:to="loc_ktos_PropertyPlantandEquipmentandFinanceLeaseRightofUseAssetafterAccumulatedDepreciationandAmortization_1053C62E7C6068496955641E78032E24" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_099CECA0E66D3E6CB123640D3B03E6FF" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_5F5A8D538E632D0D7836640D3B03FF37" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_099CECA0E66D3E6CB123640D3B03E6FF" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_DepreciationAndAmortizationOfLeasedAssets" xlink:label="loc_ktos_DepreciationAndAmortizationOfLeasedAssets_C7A8DD8560E1E394E33D640D3B0366F7" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_5F5A8D538E632D0D7836640D3B03FF37" xlink:to="loc_ktos_DepreciationAndAmortizationOfLeasedAssets_C7A8DD8560E1E394E33D640D3B0366F7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/BalanceSheetDetailsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/ConsolidatedBalanceSheets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/ConsolidatedStatementsOfCashFlows" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/ConsolidatedStatementsOfComprehensiveIncomeLoss" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/ConsolidatedStatementsOfOperations" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_18A45BA3888B21886759684428F051AE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_StatementTable_18A45BA3888B21886759684428F051AE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srt_ProductOrServiceAxis_75CF232AACD3A9014B6B684428F01C55" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_18A45BA3888B21886759684428F051AE" xlink:to="loc_srt_ProductOrServiceAxis_75CF232AACD3A9014B6B684428F01C55" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_D8BC87A6124E3A8D6B2C684428F1DB8E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_75CF232AACD3A9014B6B684428F01C55" xlink:to="loc_srt_ProductsAndServicesDomain_D8BC87A6124E3A8D6B2C684428F1DB8E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_D8BC87A6124E3A8D6B2C684428F1DB8E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_75CF232AACD3A9014B6B684428F01C55" xlink:to="loc_srt_ProductsAndServicesDomain_D8BC87A6124E3A8D6B2C684428F1DB8E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ServiceMember" xlink:label="loc_us-gaap_ServiceMember_1572B0027F927101511F684428F1613D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_D8BC87A6124E3A8D6B2C684428F1DB8E" xlink:to="loc_us-gaap_ServiceMember_1572B0027F927101511F684428F1613D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProductMember" xlink:label="loc_us-gaap_ProductMember_8C7F0957B27ABB8283ED684428F1D246" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_D8BC87A6124E3A8D6B2C684428F1DB8E" xlink:to="loc_us-gaap_ProductMember_8C7F0957B27ABB8283ED684428F1D246" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_AED3A1204C7391054AC3684428F29F72" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_AED3A1204C7391054AC3684428F29F72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CostOfGoodsAndServicesSold" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_255C70C0E459F370899A684428F2AF23" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_255C70C0E459F370899A684428F2AF23" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GrossProfit" xlink:label="loc_us-gaap_GrossProfit_ACF4D9DE1F837EF7E9A0684428F22F69" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_GrossProfit_ACF4D9DE1F837EF7E9A0684428F22F69" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_C12E8FAA375DB5EBB056684428F3304B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_C12E8FAA375DB5EBB056684428F3304B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_B63A63B9006D5B4100FA684428F3B750" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_B63A63B9006D5B4100FA684428F3B750" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_CBC48263D4578C21906A684428F30030" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_CBC48263D4578C21906A684428F30030" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetImpairment" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetImpairment_B4BD02A8771D9E7050BF684428F34F71" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_GoodwillAndIntangibleAssetImpairment_B4BD02A8771D9E7050BF684428F34F71" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_ImpairmentChargesAndAdjustmentsToUnusedOfficeSpaceLiability" xlink:label="loc_ktos_ImpairmentChargesAndAdjustmentsToUnusedOfficeSpaceLiability_CC8DA43765834A845185684428F4BAAC" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_ktos_ImpairmentChargesAndAdjustmentsToUnusedOfficeSpaceLiability_CC8DA43765834A845185684428F4BAAC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_3A5B2085D3B4940117D2684428F4D624" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_OperatingIncomeLoss_3A5B2085D3B4940117D2684428F4D624" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpenseAbstract" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_D727E7A03D2182113C8B684428F4DF42" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_D727E7A03D2182113C8B684428F4DF42" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_D33E533B79963C5835DB684428F552C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_D727E7A03D2182113C8B684428F4DF42" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_D33E533B79963C5835DB684428F552C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_19DE62819FF1085209D6684428F57F93" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_D727E7A03D2182113C8B684428F4DF42" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_19DE62819FF1085209D6684428F57F93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_D8495CBBC8D663098BF2684428F546F1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_D727E7A03D2182113C8B684428F4DF42" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_D8495CBBC8D663098BF2684428F546F1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_24DEEE20EC0BADC4D6F4684428F6F53B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_D727E7A03D2182113C8B684428F4DF42" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_24DEEE20EC0BADC4D6F4684428F6F53B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_CDF34A445BF7991270EB684428F67C9A" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_CDF34A445BF7991270EB684428F67C9A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_E081E1C2AAE0E57E8ADE684428F64C19" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_E081E1C2AAE0E57E8ADE684428F64C19" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_08066AAC02A33211DA4E684428F6288A" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_08066AAC02A33211DA4E684428F6288A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_7E2B80A640845BEABE45684428F64C91" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_7E2B80A640845BEABE45684428F64C91" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation" xlink:label="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_FEBF42D4DFB3943C8392684428F77E8D" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_FEBF42D4DFB3943C8392684428F77E8D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_FCD5F110AF898C1F14C6684428F7B1C4" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_FCD5F110AF898C1F14C6684428F7B1C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_C3D3375D43EB98CFB446684428F792F0" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_ProfitLoss_C3D3375D43EB98CFB446684428F792F0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_31D8BD2F7FDADAB8DD19684428F8E6E3" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_31D8BD2F7FDADAB8DD19684428F8E6E3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_90FD614090E35A169925684428F8B19E" xlink:type="locator" />
    <link:definitionArc order="19" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_NetIncomeLoss_90FD614090E35A169925684428F8B19E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasicAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_481802DCF86DBA870817684428F84494" xlink:type="locator" />
    <link:definitionArc order="20" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_481802DCF86DBA870817684428F84494" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsPerBasicShare" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicShare_57362C00ADC00D314340684428F86A8E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_481802DCF86DBA870817684428F84494" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicShare_57362C00ADC00D314340684428F86A8E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare_2BFAC01CFE67C144D38F684428F985E6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_481802DCF86DBA870817684428F84494" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare_2BFAC01CFE67C144D38F684428F985E6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_FE36FDC79A8D10203821684428F9A7A1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_481802DCF86DBA870817684428F84494" xlink:to="loc_us-gaap_EarningsPerShareBasic_FE36FDC79A8D10203821684428F9A7A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDilutedAbstract" xlink:label="loc_us-gaap_EarningsPerShareDilutedAbstract_595E701738D86BC7CD29684428F9B556" xlink:type="locator" />
    <link:definitionArc order="21" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_EarningsPerShareDilutedAbstract_595E701738D86BC7CD29684428F9B556" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_78C94D11B6610B41FFA4684428F9BD93" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_595E701738D86BC7CD29684428F9B556" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_78C94D11B6610B41FFA4684428F9BD93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare_3A7C7EF241A7AC2A7BC5684428FA0D63" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_595E701738D86BC7CD29684428F9B556" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare_3A7C7EF241A7AC2A7BC5684428FA0D63" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_EE2469ECC8D76EBC0D31684428FADC22" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_595E701738D86BC7CD29684428F9B556" xlink:to="loc_us-gaap_EarningsPerShareDiluted_EE2469ECC8D76EBC0D31684428FADC22" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_5A2787CC6FE8A88A42B8684428FABF47" xlink:type="locator" />
    <link:definitionArc order="22" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_795F4E782CC02D670629684428F2F9FC" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_5A2787CC6FE8A88A42B8684428FABF47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_D529F3908A2B4524E1A6684428FA140E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_5A2787CC6FE8A88A42B8684428FABF47" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_D529F3908A2B4524E1A6684428FA140E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_2479A1FBE68261D2D611684428FB2F97" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_5A2787CC6FE8A88A42B8684428FABF47" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_2479A1FBE68261D2D611684428FB2F97" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/ConsolidatedStatementsOfOperationsParenthetical" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/ConsolidatedStatementsOfStockholdersEquity" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_6C348001FDC4E434133F653FDB31C631" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1515E3B97AAA2E67774C653FDB2E0A3D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_6C348001FDC4E434133F653FDB31C631" xlink:to="loc_us-gaap_StatementTable_1515E3B97AAA2E67774C653FDB2E0A3D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_8EEE9E60558922B0E0AD653FDB2E3229" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1515E3B97AAA2E67774C653FDB2E0A3D" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_8EEE9E60558922B0E0AD653FDB2E3229" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_CC798C31DA57A05FA3DD653FDB2F906E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_8EEE9E60558922B0E0AD653FDB2E3229" xlink:to="loc_us-gaap_EquityComponentDomain_CC798C31DA57A05FA3DD653FDB2F906E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_CC798C31DA57A05FA3DD653FDB2F906E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_8EEE9E60558922B0E0AD653FDB2E3229" xlink:to="loc_us-gaap_EquityComponentDomain_CC798C31DA57A05FA3DD653FDB2F906E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="loc_us-gaap_NoncontrollingInterestMember_7496D7D6781AB8B9017D653FDB2F20B8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_CC798C31DA57A05FA3DD653FDB2F906E" xlink:to="loc_us-gaap_NoncontrollingInterestMember_7496D7D6781AB8B9017D653FDB2F20B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_94DF58E11D8A0FB2F3AB653FDB2FA1BA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_CC798C31DA57A05FA3DD653FDB2F906E" xlink:to="loc_us-gaap_CommonStockMember_94DF58E11D8A0FB2F3AB653FDB2FA1BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_56F000A32835A85E42F0653FDB2F395C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_CC798C31DA57A05FA3DD653FDB2F906E" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_56F000A32835A85E42F0653FDB2F395C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_40479909B689621E8B9C653FDB30316E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_CC798C31DA57A05FA3DD653FDB2F906E" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_40479909B689621E8B9C653FDB30316E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaap_RetainedEarningsMember_022B5DE901C3D0AF56CD653FDB30FA5D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_CC798C31DA57A05FA3DD653FDB2F906E" xlink:to="loc_us-gaap_RetainedEarningsMember_022B5DE901C3D0AF56CD653FDB30FA5D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_336375486D8E00303F69653FDB30EB90" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1515E3B97AAA2E67774C653FDB2E0A3D" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_336375486D8E00303F69653FDB30EB90" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_AC1C9C9823B1A96D66CD653FDB30AB1F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_336375486D8E00303F69653FDB30EB90" xlink:to="loc_us-gaap_TypeOfAdoptionMember_AC1C9C9823B1A96D66CD653FDB30AB1F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_AC1C9C9823B1A96D66CD653FDB30AB1F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_336375486D8E00303F69653FDB30EB90" xlink:to="loc_us-gaap_TypeOfAdoptionMember_AC1C9C9823B1A96D66CD653FDB30AB1F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountingStandardsUpdate201409Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201409Member_DFB7AE84809FA56F8B46653FDB3144E5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_AC1C9C9823B1A96D66CD653FDB30AB1F" xlink:to="loc_us-gaap_AccountingStandardsUpdate201409Member_DFB7AE84809FA56F8B46653FDB3144E5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6C348001FDC4E434133F653FDB31C631" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_A30ED39EACD376BB0D41653FDB319B25" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_A30ED39EACD376BB0D41653FDB319B25" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_CC5936C9D5B251CE6A59653FDB32DF76" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_CC5936C9D5B251CE6A59653FDB32DF76" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:label="loc_us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption_FCC2ECB526C7BB6326D2653FDB326B72" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption_FCC2ECB526C7BB6326D2653FDB326B72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_3A55DFFE654508FDCC7B653FDB32239A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_3A55DFFE654508FDCC7B653FDB32239A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_30B8D4259B1357CC378F653FDB3289A1" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_30B8D4259B1357CC378F653FDB3289A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_B8C8BDC4942C2BB4A560653FDB326A7A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_B8C8BDC4942C2BB4A560653FDB326A7A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_FD27DADD6EC24EEA7DDF653FDB33EC87" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_FD27DADD6EC24EEA7DDF653FDB33EC87" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_3C72D3C94DDBB622BEF5653FDB339F9F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_3C72D3C94DDBB622BEF5653FDB339F9F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings" xlink:label="loc_us-gaap_RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings_3D3EDD3F1C64E219CD62653FDB33FD62" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings_3D3EDD3F1C64E219CD62653FDB33FD62" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings" xlink:label="loc_us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings_30D1A09C431F81595B7D653FDB331945" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings_30D1A09C431F81595B7D653FDB331945" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_277F731284AB35CF38C7653FDB332026" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_277F731284AB35CF38C7653FDB332026" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_8163381565826A046562653FDB33E133" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_8163381565826A046562653FDB33E133" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_BC53BF7F2E95BFCE2EF9653FDB3489D2" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_NetIncomeLoss_BC53BF7F2E95BFCE2EF9653FDB3489D2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_8A8E32389E4022A72A71653FDB3440BD" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_B1E6DF22CD8507B35293653FDB31D1F7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_8A8E32389E4022A72A71653FDB3440BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInTemporaryEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_A21FFBE21C36733AFD4B653FDB34B776" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6C348001FDC4E434133F653FDB31C631" xlink:to="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_A21FFBE21C36733AFD4B653FDB34B776" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_5037A7DEB96D65252199653FDB34F53A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_A21FFBE21C36733AFD4B653FDB34B776" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_5037A7DEB96D65252199653FDB34F53A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TemporaryEquityNetIncome" xlink:label="loc_us-gaap_TemporaryEquityNetIncome_CB2319A2CE3890E11594655E251D3C18" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_A21FFBE21C36733AFD4B653FDB34B776" xlink:to="loc_us-gaap_TemporaryEquityNetIncome_CB2319A2CE3890E11594655E251D3C18" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_TemporaryEquityIncreasefromBusinessCombination" xlink:label="loc_ktos_TemporaryEquityIncreasefromBusinessCombination_986DB5C74A62211E8E5265604CC3CD83" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_A21FFBE21C36733AFD4B653FDB34B776" xlink:to="loc_ktos_TemporaryEquityIncreasefromBusinessCombination_986DB5C74A62211E8E5265604CC3CD83" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/CoverPage" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/Debt" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/DebtCreditAndSecurityAgreementDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLineItems" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_A326D8C10CBC6DA4BA865FD2E149861D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityTable" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_C68871ABA5919790FA285FD2E14308D2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A326D8C10CBC6DA4BA865FD2E149861D" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_C68871ABA5919790FA285FD2E14308D2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_290E5C41220FE2B0732E5FD2E1444CEB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_C68871ABA5919790FA285FD2E14308D2" xlink:to="loc_us-gaap_CreditFacilityAxis_290E5C41220FE2B0732E5FD2E1444CEB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_5E4283762547EC1E70A95FD2E1441912_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_290E5C41220FE2B0732E5FD2E1444CEB" xlink:to="loc_us-gaap_CreditFacilityDomain_5E4283762547EC1E70A95FD2E1441912_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_5E4283762547EC1E70A95FD2E1441912" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_290E5C41220FE2B0732E5FD2E1444CEB" xlink:to="loc_us-gaap_CreditFacilityDomain_5E4283762547EC1E70A95FD2E1441912" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_0255E5C01D80460FFAFD5FD2E1448749" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5E4283762547EC1E70A95FD2E1441912" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_0255E5C01D80460FFAFD5FD2E1448749" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LetterOfCreditMember" xlink:label="loc_us-gaap_LetterOfCreditMember_696D4FB0D2A5B40AF5495FD2E1454835" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5E4283762547EC1E70A95FD2E1441912" xlink:to="loc_us-gaap_LetterOfCreditMember_696D4FB0D2A5B40AF5495FD2E1454835" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_SwingLineLoanMember" xlink:label="loc_ktos_SwingLineLoanMember_DF89949C2F3E83A21F9D5FD2E145A71E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5E4283762547EC1E70A95FD2E1441912" xlink:to="loc_ktos_SwingLineLoanMember_DF89949C2F3E83A21F9D5FD2E145A71E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="loc_us-gaap_VariableRateAxis_59B54837CD254FE8E4595FD2E1452CA9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_C68871ABA5919790FA285FD2E14308D2" xlink:to="loc_us-gaap_VariableRateAxis_59B54837CD254FE8E4595FD2E1452CA9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_305DC4D35565263C8C7B5FD2E145BBA1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_59B54837CD254FE8E4595FD2E1452CA9" xlink:to="loc_us-gaap_VariableRateDomain_305DC4D35565263C8C7B5FD2E145BBA1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_305DC4D35565263C8C7B5FD2E145BBA1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_59B54837CD254FE8E4595FD2E1452CA9" xlink:to="loc_us-gaap_VariableRateDomain_305DC4D35565263C8C7B5FD2E145BBA1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FederalFundsEffectiveSwapRateMember" xlink:label="loc_us-gaap_FederalFundsEffectiveSwapRateMember_6C52288991C10BD417905FD2E14699D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_305DC4D35565263C8C7B5FD2E145BBA1" xlink:to="loc_us-gaap_FederalFundsEffectiveSwapRateMember_6C52288991C10BD417905FD2E14699D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_FDE773313E1D49C48CB55FD2E146CA16" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_305DC4D35565263C8C7B5FD2E145BBA1" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_FDE773313E1D49C48CB55FD2E146CA16" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BaseRateMember" xlink:label="loc_us-gaap_BaseRateMember_2E3B808F7CBE68BC91545FD2E14658BC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_305DC4D35565263C8C7B5FD2E145BBA1" xlink:to="loc_us-gaap_BaseRateMember_2E3B808F7CBE68BC91545FD2E14658BC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EurodollarMember" xlink:label="loc_us-gaap_EurodollarMember_04CC4E9554EB9BEB82E55FD2E146C2DA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_305DC4D35565263C8C7B5FD2E145BBA1" xlink:to="loc_us-gaap_EurodollarMember_04CC4E9554EB9BEB82E55FD2E146C2DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_EBAB70B39249082EFA735FD2E147FDFA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_C68871ABA5919790FA285FD2E14308D2" xlink:to="loc_srt_RangeAxis_EBAB70B39249082EFA735FD2E147FDFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_AEA83B672EB1BD397FB35FD2E14701A1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_EBAB70B39249082EFA735FD2E147FDFA" xlink:to="loc_srt_RangeMember_AEA83B672EB1BD397FB35FD2E14701A1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_AEA83B672EB1BD397FB35FD2E14701A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_EBAB70B39249082EFA735FD2E147FDFA" xlink:to="loc_srt_RangeMember_AEA83B672EB1BD397FB35FD2E14701A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_FE49231AFB12D08377195FD2E148E95C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_AEA83B672EB1BD397FB35FD2E14701A1" xlink:to="loc_srt_MinimumMember_FE49231AFB12D08377195FD2E148E95C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_96D467E1D01ADA163F145FD2E14881D3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_AEA83B672EB1BD397FB35FD2E14701A1" xlink:to="loc_srt_MaximumMember_96D467E1D01ADA163F145FD2E14881D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_21744B3760C6FB1161335FD2E1489FFE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_C68871ABA5919790FA285FD2E14308D2" xlink:to="loc_us-gaap_DebtInstrumentAxis_21744B3760C6FB1161335FD2E1489FFE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7FE826B9C760B3E6150A5FD2E1480595_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_21744B3760C6FB1161335FD2E1489FFE" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7FE826B9C760B3E6150A5FD2E1480595_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7FE826B9C760B3E6150A5FD2E1480595" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_21744B3760C6FB1161335FD2E1489FFE" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7FE826B9C760B3E6150A5FD2E1480595" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_AmendmentCreditAgreementMember" xlink:label="loc_ktos_AmendmentCreditAgreementMember_C30FFDDFE5C1434DB9B95FD2E149A75D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7FE826B9C760B3E6150A5FD2E1480595" xlink:to="loc_ktos_AmendmentCreditAgreementMember_C30FFDDFE5C1434DB9B95FD2E149A75D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_6BAEC847927F3375BBBA5FD2E14AAAC5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A326D8C10CBC6DA4BA865FD2E149861D" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_6BAEC847927F3375BBBA5FD2E14AAAC5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTerm" xlink:label="loc_us-gaap_DebtInstrumentTerm_9EB54C66621C4A017DEE5FD2E14AEC1C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A326D8C10CBC6DA4BA865FD2E149861D" xlink:to="loc_us-gaap_DebtInstrumentTerm_9EB54C66621C4A017DEE5FD2E14AEC1C" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_LineOfCreditFacilityMaximumPossibleBorrowingsSubjectToApplicationAndBankApproval" xlink:label="loc_ktos_LineOfCreditFacilityMaximumPossibleBorrowingsSubjectToApplicationAndBankApproval_A2A2F9AD59F17DA1B1DE5FD2E14A6CDC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A326D8C10CBC6DA4BA865FD2E149861D" xlink:to="loc_ktos_LineOfCreditFacilityMaximumPossibleBorrowingsSubjectToApplicationAndBankApproval_A2A2F9AD59F17DA1B1DE5FD2E14A6CDC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_00AC857E7AA2A5D543645FD2E14A2C29" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A326D8C10CBC6DA4BA865FD2E149861D" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_00AC857E7AA2A5D543645FD2E14A2C29" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_LineofCreditFacilityCovenantTermsMinimumPercentageofBorrowingBaseorTotalCommitmentAmount" xlink:label="loc_ktos_LineofCreditFacilityCovenantTermsMinimumPercentageofBorrowingBaseorTotalCommitmentAmount_E49213D177556A6CB9835FD2E14B4C35" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A326D8C10CBC6DA4BA865FD2E149861D" xlink:to="loc_ktos_LineofCreditFacilityCovenantTermsMinimumPercentageofBorrowingBaseorTotalCommitmentAmount_E49213D177556A6CB9835FD2E14B4C35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCredit" xlink:label="loc_us-gaap_LineOfCredit_C19E2940AA5D10451DEA5FD2E14B52BD" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A326D8C10CBC6DA4BA865FD2E149861D" xlink:to="loc_us-gaap_LineOfCredit_C19E2940AA5D10451DEA5FD2E14B52BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_C53C65331EFDDE04E5795FD2E14B566B" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A326D8C10CBC6DA4BA865FD2E149861D" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_C53C65331EFDDE04E5795FD2E14B566B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/DebtFairValueOfLongTermDebtDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/DebtIssuanceOf65SeniorSecuredNotesDue2025Details" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_90327D78D865C352D72FEBB2869CA8E8" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_2EFFE5A7DC4A3D6D3CDEEBB2869902CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_90327D78D865C352D72FEBB2869CA8E8" xlink:to="loc_us-gaap_DebtInstrumentTable_2EFFE5A7DC4A3D6D3CDEEBB2869902CA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_B66166465CEB990B21AEEBB2869A7DDF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_2EFFE5A7DC4A3D6D3CDEEBB2869902CA" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_B66166465CEB990B21AEEBB2869A7DDF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_D1013A59A22D312B06C0EBB2869ACDDD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_B66166465CEB990B21AEEBB2869A7DDF" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_D1013A59A22D312B06C0EBB2869ACDDD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_D1013A59A22D312B06C0EBB2869ACDDD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_B66166465CEB990B21AEEBB2869A7DDF" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_D1013A59A22D312B06C0EBB2869ACDDD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_80D70873B59BA6541879EBB2869A742A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_D1013A59A22D312B06C0EBB2869ACDDD" xlink:to="loc_us-gaap_SeniorNotesMember_80D70873B59BA6541879EBB2869A742A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_B2C23FE2AA3340A49A55EBB2869ABEC9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_2EFFE5A7DC4A3D6D3CDEEBB2869902CA" xlink:to="loc_us-gaap_DebtInstrumentAxis_B2C23FE2AA3340A49A55EBB2869ABEC9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_18E1DC7730578ABEB159EBB2869B5CC0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_B2C23FE2AA3340A49A55EBB2869ABEC9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_18E1DC7730578ABEB159EBB2869B5CC0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_18E1DC7730578ABEB159EBB2869B5CC0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_B2C23FE2AA3340A49A55EBB2869ABEC9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_18E1DC7730578ABEB159EBB2869B5CC0" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_SixPointFivePercentSeniorSecuredNotesDue2025Member" xlink:label="loc_ktos_SixPointFivePercentSeniorSecuredNotesDue2025Member_7A5220E1DF936B794239EBB2869BB94F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_18E1DC7730578ABEB159EBB2869B5CC0" xlink:to="loc_ktos_SixPointFivePercentSeniorSecuredNotesDue2025Member_7A5220E1DF936B794239EBB2869BB94F" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_SevenPercentSeniorNotesDue2019Member" xlink:label="loc_ktos_SevenPercentSeniorNotesDue2019Member_7356665E3B2D740187FBEBB2869B2452" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_18E1DC7730578ABEB159EBB2869B5CC0" xlink:to="loc_ktos_SevenPercentSeniorNotesDue2019Member_7356665E3B2D740187FBEBB2869B2452" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_EF79BA60D439DB411F52EBB2869B274A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_2EFFE5A7DC4A3D6D3CDEEBB2869902CA" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_EF79BA60D439DB411F52EBB2869B274A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_F14ED26055034F21A9D6EBB2869B657D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_EF79BA60D439DB411F52EBB2869B274A" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_F14ED26055034F21A9D6EBB2869B657D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_F14ED26055034F21A9D6EBB2869B657D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_EF79BA60D439DB411F52EBB2869B274A" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_F14ED26055034F21A9D6EBB2869B657D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_12AC90E7E2F7DF2ED40AEBB2869C736E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_F14ED26055034F21A9D6EBB2869B657D" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_12AC90E7E2F7DF2ED40AEBB2869C736E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_F5DCE894E4D617169BABEBB2869C0A95" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_F14ED26055034F21A9D6EBB2869B657D" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_F5DCE894E4D617169BABEBB2869C0A95" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_57E68B043497495DBDD0EBB2869C662D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_90327D78D865C352D72FEBB2869CA8E8" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_57E68B043497495DBDD0EBB2869C662D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_F8A21B04A732AD61BBD5EBB2869DFFB7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_90327D78D865C352D72FEBB2869CA8E8" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_F8A21B04A732AD61BBD5EBB2869DFFB7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredFinanceCostsGross" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_57273470BC9FE53A3217EBB2869D2D01" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_90327D78D865C352D72FEBB2869CA8E8" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_57273470BC9FE53A3217EBB2869D2D01" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRepurchaseAmount" xlink:label="loc_us-gaap_DebtInstrumentRepurchaseAmount_3CBA56D5EA64D4E0B21EEBB2869DB89F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_90327D78D865C352D72FEBB2869CA8E8" xlink:to="loc_us-gaap_DebtInstrumentRepurchaseAmount_3CBA56D5EA64D4E0B21EEBB2869DB89F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentUnamortizedPremium" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedPremium_4DC38B542F6A56D9DB6BEBB2869D5BDF" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_90327D78D865C352D72FEBB2869CA8E8" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedPremium_4DC38B542F6A56D9DB6BEBB2869D5BDF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentIncreaseAccruedInterest" xlink:label="loc_us-gaap_DebtInstrumentIncreaseAccruedInterest_02677D7D0F2B92201739EBB2869D8576" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_90327D78D865C352D72FEBB2869CA8E8" xlink:to="loc_us-gaap_DebtInstrumentIncreaseAccruedInterest_02677D7D0F2B92201739EBB2869D8576" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_EBFF109769206B712846EBB2869D8DD9" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_90327D78D865C352D72FEBB2869CA8E8" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_EBFF109769206B712846EBB2869D8DD9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_2053CB9EE745177508B0EBB2869D5DD9" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_90327D78D865C352D72FEBB2869CA8E8" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_2053CB9EE745177508B0EBB2869D5DD9" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/DebtTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/DiscontinuedOperations" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/DiscontinuedOperationsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_EDC84FBC5ECF4C8383B377CD1F30DE6B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_EDC84FBC5ECF4C8383B377CD1F30DE6B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_599C01CADFF49CD5F2C877CD1F31B7BB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_EDC84FBC5ECF4C8383B377CD1F30DE6B" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_599C01CADFF49CD5F2C877CD1F31B7BB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_B274D4156834CD40EC5F77CD1F3102B0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_599C01CADFF49CD5F2C877CD1F31B7BB" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_B274D4156834CD40EC5F77CD1F3102B0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_B274D4156834CD40EC5F77CD1F3102B0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_599C01CADFF49CD5F2C877CD1F31B7BB" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_B274D4156834CD40EC5F77CD1F3102B0" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_PublicSafetyAndSecurityMember" xlink:label="loc_ktos_PublicSafetyAndSecurityMember_9AB01CDDC202A61E175E77CD1F31CD48" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_B274D4156834CD40EC5F77CD1F3102B0" xlink:to="loc_ktos_PublicSafetyAndSecurityMember_9AB01CDDC202A61E175E77CD1F31CD48" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_HerleyIndustriesIncMember" xlink:label="loc_ktos_HerleyIndustriesIncMember_BD6BB95778B66EF8C09977CD1F32CAE1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_B274D4156834CD40EC5F77CD1F3102B0" xlink:to="loc_ktos_HerleyIndustriesIncMember_BD6BB95778B66EF8C09977CD1F32CAE1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupClassificationAxis" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_CB5DEF868A5EDF6A2CBB77CD1F32D31B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_EDC84FBC5ECF4C8383B377CD1F30DE6B" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_CB5DEF868A5EDF6A2CBB77CD1F32D31B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_B175A8AFAB74BF0654C877CD1F3212A4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_CB5DEF868A5EDF6A2CBB77CD1F32D31B" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_B175A8AFAB74BF0654C877CD1F3212A4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_B175A8AFAB74BF0654C877CD1F3212A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_CB5DEF868A5EDF6A2CBB77CD1F32D31B" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_B175A8AFAB74BF0654C877CD1F3212A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember" xlink:label="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_B5C237C8DDDAF87B29B877CD1F32A4A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_B175A8AFAB74BF0654C877CD1F3212A4" xlink:to="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_B5C237C8DDDAF87B29B877CD1F32A4A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DiscontinuedOperationsDisposedOfBySaleMember" xlink:label="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_C042A7955113CC51C61377CD1F33C61A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_B175A8AFAB74BF0654C877CD1F3212A4" xlink:to="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_C042A7955113CC51C61377CD1F33C61A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_045D1FB665B98F92EAEF77CD1F330EA2" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_EDC84FBC5ECF4C8383B377CD1F30DE6B" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_045D1FB665B98F92EAEF77CD1F330EA2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_3C2B5358F45630184C5A77CD1F335829_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_045D1FB665B98F92EAEF77CD1F330EA2" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_3C2B5358F45630184C5A77CD1F335829_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_3C2B5358F45630184C5A77CD1F335829" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_045D1FB665B98F92EAEF77CD1F330EA2" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_3C2B5358F45630184C5A77CD1F335829" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_FA219B83D5ECF42E89FD77CD1F34F46A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_3C2B5358F45630184C5A77CD1F335829" xlink:to="loc_us-gaap_SeniorNotesMember_FA219B83D5ECF42E89FD77CD1F34F46A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_F76AC3A572F5CAD38FF277CD1F340CCE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_EDC84FBC5ECF4C8383B377CD1F30DE6B" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_F76AC3A572F5CAD38FF277CD1F340CCE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_8235455E19C927C0085177CD1F346366_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_F76AC3A572F5CAD38FF277CD1F340CCE" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_8235455E19C927C0085177CD1F346366_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_8235455E19C927C0085177CD1F346366" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_F76AC3A572F5CAD38FF277CD1F340CCE" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_8235455E19C927C0085177CD1F346366" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_51F6C4367C979BF82E5277CD1F3522EA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_8235455E19C927C0085177CD1F346366" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_51F6C4367C979BF82E5277CD1F3522EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_D50CE540B08C6A43C11777CD1F35ED26" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_EDC84FBC5ECF4C8383B377CD1F30DE6B" xlink:to="loc_us-gaap_DebtInstrumentAxis_D50CE540B08C6A43C11777CD1F35ED26" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_82C1874795223001BB2477CD1F350437_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_D50CE540B08C6A43C11777CD1F35ED26" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_82C1874795223001BB2477CD1F350437_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_82C1874795223001BB2477CD1F350437" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_D50CE540B08C6A43C11777CD1F35ED26" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_82C1874795223001BB2477CD1F350437" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_SixPointFivePercentSeniorSecuredNotesDue2025Member" xlink:label="loc_ktos_SixPointFivePercentSeniorSecuredNotesDue2025Member_C8DDADEF6C4AD11FD6B077CD1F365B8C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_82C1874795223001BB2477CD1F350437" xlink:to="loc_ktos_SixPointFivePercentSeniorSecuredNotesDue2025Member_C8DDADEF6C4AD11FD6B077CD1F365B8C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_9939F397F867047FC0B277CD1F36CE5A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_9939F397F867047FC0B277CD1F36CE5A" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationWorkingCapitalAdjustment" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationWorkingCapitalAdjustment_ECAA11C01D1B934DE79177CD1F36499D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationWorkingCapitalAdjustment_ECAA11C01D1B934DE79177CD1F36499D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_2027EED5A66ED5C1E76477CD1F3756CD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_2027EED5A66ED5C1E76477CD1F3756CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_BA3EB6D0D01198C5F5EE77CD1F37E5FF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_BA3EB6D0D01198C5F5EE77CD1F37E5FF" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationGainFromTaxLiability" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationGainFromTaxLiability_F4594834838C1FBBF57077CD1F378DE9" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationGainFromTaxLiability_F4594834838C1FBBF57077CD1F378DE9" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationImpactOnRevenueOfProjectCostAdjustments" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationImpactOnRevenueOfProjectCostAdjustments_DFC837909DC9222D70C977CD1F37D8E3" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationImpactOnRevenueOfProjectCostAdjustments_DFC837909DC9222D70C977CD1F37D8E3" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationTransactionRelatedCost" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationTransactionRelatedCost_7D402D9E216289EF19E877CD1F38C836" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationTransactionRelatedCost_7D402D9E216289EF19E877CD1F38C836" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationDepreciationAndAmortization" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationDepreciationAndAmortization_F957F8EBEAAA5693D1CA77CD1F38983C" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationDepreciationAndAmortization_F957F8EBEAAA5693D1CA77CD1F38983C" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_DiscontinuedOperationReclassificationOfTaxEffectofDiscontinuedOperation" xlink:label="loc_ktos_DiscontinuedOperationReclassificationOfTaxEffectofDiscontinuedOperation_2B2807EAD5CE7E14E6DD77CD1F3807DE" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_EC73DBDEC1B4352834D077CD1F36DE69" xlink:to="loc_ktos_DiscontinuedOperationReclassificationOfTaxEffectofDiscontinuedOperation_2B2807EAD5CE7E14E6DD77CD1F3807DE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/DiscontinuedOperationsResultsOfDiscontinuedOperationsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A086D136DE31D98ACF2E699797BA27E6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A086D136DE31D98ACF2E699797BA27E6" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_2196ED271FA8790AE00B699797BA6FE6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A086D136DE31D98ACF2E699797BA27E6" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_2196ED271FA8790AE00B699797BA6FE6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_8ABBAAA25488176A386C699797BB71ED_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_2196ED271FA8790AE00B699797BA6FE6" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_8ABBAAA25488176A386C699797BB71ED_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_8ABBAAA25488176A386C699797BB71ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_2196ED271FA8790AE00B699797BA6FE6" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_8ABBAAA25488176A386C699797BB71ED" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_HerleyIndustriesIncMember" xlink:label="loc_ktos_HerleyIndustriesIncMember_FF10ADD9C45D0B9C625D699797BBE828" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_8ABBAAA25488176A386C699797BB71ED" xlink:to="loc_ktos_HerleyIndustriesIncMember_FF10ADD9C45D0B9C625D699797BBE828" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupClassificationAxis" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_E19C9309CCA587E70E6B699797BC4E94" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A086D136DE31D98ACF2E699797BA27E6" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_E19C9309CCA587E70E6B699797BC4E94" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_1E72AC5CBCAD6E899AC5699797BC89C6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_E19C9309CCA587E70E6B699797BC4E94" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_1E72AC5CBCAD6E899AC5699797BC89C6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_1E72AC5CBCAD6E899AC5699797BC89C6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_E19C9309CCA587E70E6B699797BC4E94" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_1E72AC5CBCAD6E899AC5699797BC89C6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DiscontinuedOperationsDisposedOfBySaleMember" xlink:label="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_5FE03E11734448A9C237699797BCA72D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_1E72AC5CBCAD6E899AC5699797BC89C6" xlink:to="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_5FE03E11734448A9C237699797BCA72D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_854D45BFEA7C2A7FF436699797BD3D80" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_854D45BFEA7C2A7FF436699797BD3D80" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold_79D7ABBE7706739FF5D5699797BD9C7C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold_79D7ABBE7706739FF5D5699797BD9C7C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense_C0D65C0AE5B972C1FB9B699797BD3346" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense_C0D65C0AE5B972C1FB9B699797BD3346" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense_A52669FCD9BE4D1E0834699797BECE9E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense_A52669FCD9BE4D1E0834699797BECE9E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodBeforeIncomeTax_EB55C245B1518C478FE8699797BE8B98" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:to="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodBeforeIncomeTax_EB55C245B1518C478FE8699797BE8B98" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_6E79FC50A54F3D065440699797BECF77" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_6E79FC50A54F3D065440699797BECF77" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_6B36B073677F89B5D148699797BE3255" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:to="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_6B36B073677F89B5D148699797BE3255" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation" xlink:label="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_8296C4005E8848A0C3B2699797BE3359" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:to="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_8296C4005E8848A0C3B2699797BE3359" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_848727B6615549EFB04C699797BFA32C" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13021114BE7CEC8C4908699797BDEB09" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_848727B6615549EFB04C699797BFA32C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/DiscontinuedOperationsSummaryOfAssetsAndLiabilitiesOfDiscontinuedOperationsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_CE763AFDD14582220DC8F0E04CB78DAF" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A4E448AF90E66355F1A6F0E04CB59BE0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_CE763AFDD14582220DC8F0E04CB78DAF" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A4E448AF90E66355F1A6F0E04CB59BE0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_952C5A53D998C807FDBFF0E04CB59906" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A4E448AF90E66355F1A6F0E04CB59BE0" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_952C5A53D998C807FDBFF0E04CB59906" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3DC12A2C3F1F7A8650C7F0E04CB5BCBD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_952C5A53D998C807FDBFF0E04CB59906" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3DC12A2C3F1F7A8650C7F0E04CB5BCBD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3DC12A2C3F1F7A8650C7F0E04CB5BCBD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_952C5A53D998C807FDBFF0E04CB59906" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3DC12A2C3F1F7A8650C7F0E04CB5BCBD" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_HerleyIndustriesIncMember" xlink:label="loc_ktos_HerleyIndustriesIncMember_21D6BA723A71163EC78BF0E04CB6118E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3DC12A2C3F1F7A8650C7F0E04CB5BCBD" xlink:to="loc_ktos_HerleyIndustriesIncMember_21D6BA723A71163EC78BF0E04CB6118E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupClassificationAxis" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_3DD865AE5262B5BE7CCEF0E04CB67DB4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A4E448AF90E66355F1A6F0E04CB59BE0" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_3DD865AE5262B5BE7CCEF0E04CB67DB4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_2BAB9F0DDE31BE79938FF0E04CB6D472_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_3DD865AE5262B5BE7CCEF0E04CB67DB4" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_2BAB9F0DDE31BE79938FF0E04CB6D472_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_2BAB9F0DDE31BE79938FF0E04CB6D472" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_3DD865AE5262B5BE7CCEF0E04CB67DB4" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_2BAB9F0DDE31BE79938FF0E04CB6D472" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DiscontinuedOperationsDisposedOfBySaleMember" xlink:label="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_B6BB944D5D8A46C0B285F0E04CB6760D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_2BAB9F0DDE31BE79938FF0E04CB6D472" xlink:to="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_B6BB944D5D8A46C0B285F0E04CB6760D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet_C18E3C1CF272991B99D3F0E04CB70A52" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_CE763AFDD14582220DC8F0E04CB78DAF" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet_C18E3C1CF272991B99D3F0E04CB70A52" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets_DF5FB7ED91DF62EB5E10F0E04CB7C523" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_CE763AFDD14582220DC8F0E04CB78DAF" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets_DF5FB7ED91DF62EB5E10F0E04CB7C523" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent" xlink:label="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent_967FC7912528CECF1D25F0E04CB83863" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_CE763AFDD14582220DC8F0E04CB78DAF" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent_967FC7912528CECF1D25F0E04CB83863" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayableCurrent" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayableCurrent_019340E5541BADC01CD9F0E04CB80219" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_CE763AFDD14582220DC8F0E04CB78DAF" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayableCurrent_019340E5541BADC01CD9F0E04CB80219" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilitiesCurrent" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilitiesCurrent_C18D23C4DEC9A425F81DF0E04CB984BD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_CE763AFDD14582220DC8F0E04CB78DAF" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilitiesCurrent_C18D23C4DEC9A425F81DF0E04CB984BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities_CBCEE10FC3D967D7F734F0E04CB9B05F" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_CE763AFDD14582220DC8F0E04CB78DAF" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities_CBCEE10FC3D967D7F734F0E04CB9B05F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent_702CC1E240BC4C4F57C3F0E04CB9754D" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_CE763AFDD14582220DC8F0E04CB78DAF" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent_702CC1E240BC4C4F57C3F0E04CB9754D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities_798F27F224814B47DCCCF0E04CB9B9CE" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_CE763AFDD14582220DC8F0E04CB78DAF" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities_798F27F224814B47DCCCF0E04CB9B9CE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/DiscontinuedOperationsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/FairValueMeasurement" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/GoodwillAndOtherIntangibleAssets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/GoodwillAndOtherIntangibleAssetsGoodwillDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillLineItems" xlink:label="loc_us-gaap_GoodwillLineItems_CD747BA21C0553BC1DA55FE07687B646" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfGoodwillTable" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_8DC9A447E4EFC976A1B25FE07685E9F4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_CD747BA21C0553BC1DA55FE07687B646" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_8DC9A447E4EFC976A1B25FE07685E9F4" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_AD92DA408FD8B83883BF5FE07686B4BE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_8DC9A447E4EFC976A1B25FE07685E9F4" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_AD92DA408FD8B83883BF5FE07686B4BE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_A613899AD9FC9CE2CB4E5FE076861ADF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_AD92DA408FD8B83883BF5FE07686B4BE" xlink:to="loc_us-gaap_SegmentDomain_A613899AD9FC9CE2CB4E5FE076861ADF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_A613899AD9FC9CE2CB4E5FE076861ADF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_AD92DA408FD8B83883BF5FE07686B4BE" xlink:to="loc_us-gaap_SegmentDomain_A613899AD9FC9CE2CB4E5FE076861ADF" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_KratosUnmannedSystemsMember" xlink:label="loc_ktos_KratosUnmannedSystemsMember_CF70FEB6D89E74A55AFA5FE07687DCA3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_A613899AD9FC9CE2CB4E5FE076861ADF" xlink:to="loc_ktos_KratosUnmannedSystemsMember_CF70FEB6D89E74A55AFA5FE07687DCA3" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_KratosGovernmentSolutionsMember" xlink:label="loc_ktos_KratosGovernmentSolutionsMember_E969DFF63F0726C60AF35FE07687ABAF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_A613899AD9FC9CE2CB4E5FE076861ADF" xlink:to="loc_ktos_KratosGovernmentSolutionsMember_E969DFF63F0726C60AF35FE07687ABAF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NumberOfOperatingSegments" xlink:label="loc_us-gaap_NumberOfOperatingSegments_D64F51041768008752B55FE076870623" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_CD747BA21C0553BC1DA55FE07687B646" xlink:to="loc_us-gaap_NumberOfOperatingSegments_D64F51041768008752B55FE076870623" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_515E574FAD60A99632445FE07688CABC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_CD747BA21C0553BC1DA55FE07687B646" xlink:to="loc_us-gaap_Goodwill_515E574FAD60A99632445FE07688CABC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillImpairmentLoss" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_AA0C9D72A0AAA8F14B595FE07688867D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_CD747BA21C0553BC1DA55FE07687B646" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_AA0C9D72A0AAA8F14B595FE07688867D" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_NumberOfLostContractOpportunities" xlink:label="loc_ktos_NumberOfLostContractOpportunities_E1173890296F1A9CE52C5FE07688E452" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_CD747BA21C0553BC1DA55FE07687B646" xlink:to="loc_ktos_NumberOfLostContractOpportunities_E1173890296F1A9CE52C5FE07688E452" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_LostContractOpportunitiesPeriod" xlink:label="loc_ktos_LostContractOpportunitiesPeriod_07AB56509DD1A1EA212C5FE076891611" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_CD747BA21C0553BC1DA55FE07687B646" xlink:to="loc_ktos_LostContractOpportunitiesPeriod_07AB56509DD1A1EA212C5FE076891611" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillImpairedAccumulatedImpairmentLossAbstract" xlink:label="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLossAbstract_DDC0642E8C14D68F3D7F5FE076895750" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_CD747BA21C0553BC1DA55FE07687B646" xlink:to="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLossAbstract_DDC0642E8C14D68F3D7F5FE076895750" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillGross" xlink:label="loc_us-gaap_GoodwillGross_816574E27B436DBA09335FE07689515A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLossAbstract_DDC0642E8C14D68F3D7F5FE076895750" xlink:to="loc_us-gaap_GoodwillGross_816574E27B436DBA09335FE07689515A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillImpairedAccumulatedImpairmentLoss" xlink:label="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLoss_CD627CCAAF2FA72D2E6E5FE0768A0F61" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLossAbstract_DDC0642E8C14D68F3D7F5FE076895750" xlink:to="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLoss_CD627CCAAF2FA72D2E6E5FE0768A0F61" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/GoodwillAndOtherIntangibleAssetsIntangibleAssetAmortizationDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/GoodwillAndOtherIntangibleAssetsPurchasedIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_C44CA813C76D9EFBDC9D5FE59EA2E154" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_452B96A2C9695890EE2D5FE59E9F5F8E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_C44CA813C76D9EFBDC9D5FE59EA2E154" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_452B96A2C9695890EE2D5FE59E9F5F8E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_E450A3A2DFA9F42387375FE59E9FB81D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_452B96A2C9695890EE2D5FE59E9F5F8E" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_E450A3A2DFA9F42387375FE59E9FB81D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EA9AD8E3E483350501E75FE59EA0FE84_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_E450A3A2DFA9F42387375FE59E9FB81D" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EA9AD8E3E483350501E75FE59EA0FE84_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EA9AD8E3E483350501E75FE59EA0FE84" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_E450A3A2DFA9F42387375FE59E9FB81D" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EA9AD8E3E483350501E75FE59EA0FE84" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CustomerRelationshipsMember" xlink:label="loc_us-gaap_CustomerRelationshipsMember_C4ACD015CD54358A1CC65FE59EA04CDD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EA9AD8E3E483350501E75FE59EA0FE84" xlink:to="loc_us-gaap_CustomerRelationshipsMember_C4ACD015CD54358A1CC65FE59EA04CDD" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_ContractsAndBacklogMember" xlink:label="loc_ktos_ContractsAndBacklogMember_981D2909F4014A48D3545FE59EA0AC38" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EA9AD8E3E483350501E75FE59EA0FE84" xlink:to="loc_ktos_ContractsAndBacklogMember_981D2909F4014A48D3545FE59EA0AC38" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_2BE806C304809565BB7A5FE59EA1D249" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EA9AD8E3E483350501E75FE59EA0FE84" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_2BE806C304809565BB7A5FE59EA1D249" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TradeNamesMember" xlink:label="loc_us-gaap_TradeNamesMember_C4D20CD639A53D72F62F5FE59EA1B79B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EA9AD8E3E483350501E75FE59EA0FE84" xlink:to="loc_us-gaap_TradeNamesMember_C4D20CD639A53D72F62F5FE59EA1B79B" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_FavorableOperatingLeaseMember" xlink:label="loc_ktos_FavorableOperatingLeaseMember_B49460B9AA503589283A5FE59EA13903" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EA9AD8E3E483350501E75FE59EA0FE84" xlink:to="loc_ktos_FavorableOperatingLeaseMember_B49460B9AA503589283A5FE59EA13903" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_ADD8143E9CCF1949B2EB5FE59EA1A822" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_452B96A2C9695890EE2D5FE59E9F5F8E" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_ADD8143E9CCF1949B2EB5FE59EA1A822" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_5AE8C1C8741957BA92F05FE59EA2E03F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_ADD8143E9CCF1949B2EB5FE59EA1A822" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_5AE8C1C8741957BA92F05FE59EA2E03F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_5AE8C1C8741957BA92F05FE59EA2E03F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_ADD8143E9CCF1949B2EB5FE59EA1A822" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_5AE8C1C8741957BA92F05FE59EA2E03F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TradeNamesMember" xlink:label="loc_us-gaap_TradeNamesMember_1AE9873B4BD679D4CB915FE59EA25374" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_5AE8C1C8741957BA92F05FE59EA2E03F" xlink:to="loc_us-gaap_TradeNamesMember_1AE9873B4BD679D4CB915FE59EA25374" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNetAbstract" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_CC924159D18897F821485FE59EA268F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_C44CA813C76D9EFBDC9D5FE59EA2E154" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_CC924159D18897F821485FE59EA268F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_3AB9E50FC540FD5045BF5FE59EA8B292" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_CC924159D18897F821485FE59EA268F5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_3AB9E50FC540FD5045BF5FE59EA8B292" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_1589029415EE01A0C3415FE59EA84765" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_CC924159D18897F821485FE59EA268F5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_1589029415EE01A0C3415FE59EA84765" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_F8D90B24A6C44D2C07DE5FE59EA95DAB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_CC924159D18897F821485FE59EA268F5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_F8D90B24A6C44D2C07DE5FE59EA95DAB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_080785867C67A6C98ABB5FE59EA96FF2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_C44CA813C76D9EFBDC9D5FE59EA2E154" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_080785867C67A6C98ABB5FE59EA96FF2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_B90D36998827394FCA6F5FE59EA95850" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_C44CA813C76D9EFBDC9D5FE59EA2E154" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_B90D36998827394FCA6F5FE59EA95850" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_25F7A4B1E4D5E823200E5FE59EA94338" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_C44CA813C76D9EFBDC9D5FE59EA2E154" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_25F7A4B1E4D5E823200E5FE59EA94338" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_39180060343B74E62C215FE59EA9BBB4" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_C44CA813C76D9EFBDC9D5FE59EA2E154" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_39180060343B74E62C215FE59EA9BBB4" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/GoodwillAndOtherIntangibleAssetsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/IncomeTaxes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/IncomeTaxesComponentsOfIncomeTaxesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/IncomeTaxesDeferredTaxesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/IncomeTaxesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLossCarryforwardsLineItems" xlink:label="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLossCarryforwardsTable" xlink:label="loc_us-gaap_OperatingLossCarryforwardsTable_70CFB13E666E6B8A15D569979886B022" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_us-gaap_OperatingLossCarryforwardsTable_70CFB13E666E6B8A15D569979886B022" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_ACF72ACA684CA51B547969979887B593" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_70CFB13E666E6B8A15D569979886B022" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_ACF72ACA684CA51B547969979887B593" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_AE5C14F817DD25C7B398699798874C77_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_ACF72ACA684CA51B547969979887B593" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_AE5C14F817DD25C7B398699798874C77_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_AE5C14F817DD25C7B398699798874C77" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_ACF72ACA684CA51B547969979887B593" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_AE5C14F817DD25C7B398699798874C77" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DomesticCountryMember" xlink:label="loc_us-gaap_DomesticCountryMember_C7F282E53660031E779F6997988879CE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_AE5C14F817DD25C7B398699798874C77" xlink:to="loc_us-gaap_DomesticCountryMember_C7F282E53660031E779F6997988879CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StateAndLocalJurisdictionMember" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_E5CCBFADB01667D5BA8869979888C7A4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_AE5C14F817DD25C7B398699798874C77" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_E5CCBFADB01667D5BA8869979888C7A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount" xlink:label="loc_us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount_75C7B6B55C5AF332395069979888AB01" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount_75C7B6B55C5AF332395069979888AB01" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLossCarryforwards" xlink:label="loc_us-gaap_OperatingLossCarryforwards_217EDAB4C63D2836B311699798899579" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_us-gaap_OperatingLossCarryforwards_217EDAB4C63D2836B311699798899579" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfForeignSubsidiaries" xlink:label="loc_us-gaap_DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfForeignSubsidiaries_A7B804189F3D02CE21E46997988A6910" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_us-gaap_DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfForeignSubsidiaries_A7B804189F3D02CE21E46997988A6910" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_DeferredTaxLiabilityNotRecognizedUndistributedEarningsofForeignSubsidiariesCashandCashEquivalentsAvailableforDistribution" xlink:label="loc_ktos_DeferredTaxLiabilityNotRecognizedUndistributedEarningsofForeignSubsidiariesCashandCashEquivalentsAvailableforDistribution_67F42398B1BCF37AE2F46997988A97F7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_ktos_DeferredTaxLiabilityNotRecognizedUndistributedEarningsofForeignSubsidiariesCashandCashEquivalentsAvailableforDistribution_67F42398B1BCF37AE2F46997988A97F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_EA58FFC2A7F7494C30176997988A5494" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_EA58FFC2A7F7494C30176997988A5494" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRateDeferredTaxAssets" xlink:label="loc_ktos_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRateDeferredTaxAssets_AC68490334DF2BE903D16997988AC1F7" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_ktos_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRateDeferredTaxAssets_AC68490334DF2BE903D16997988AC1F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense_04F0D8E25D55177439286997988A92A5" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense_04F0D8E25D55177439286997988A92A5" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestBenefitReversalsOfPriorPositions" xlink:label="loc_ktos_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestBenefitReversalsOfPriorPositions_1AA8336F018885C320206997988B55B0" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_ktos_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestBenefitReversalsOfPriorPositions_1AA8336F018885C320206997988B55B0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued_BBFD9261EAC6AA974B846997988B47ED" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued_BBFD9261EAC6AA974B846997988B47ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleAmountOfUnrecordedBenefit" xlink:label="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleAmountOfUnrecordedBenefit_215D0EA03D9828D5ACAC6997988B8CBB" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_BFB622BD013EEA2DEE65699798882690" xlink:to="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleAmountOfUnrecordedBenefit_215D0EA03D9828D5ACAC6997988B8CBB" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/IncomeTaxesReconciliationOfIncomeTaxProvisionDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/IncomeTaxesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/Leases" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/LeasesAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_8F0A1E45B5B70A724C1877CD204BC9FA" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_970B2DE56F30D32FF02A77CD204AD87C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8F0A1E45B5B70A724C1877CD204BC9FA" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_970B2DE56F30D32FF02A77CD204AD87C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementGeographicalAxis" xlink:label="loc_srt_StatementGeographicalAxis_EBCD9B79334A0AC8AC6877CD204AE963" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_970B2DE56F30D32FF02A77CD204AD87C" xlink:to="loc_srt_StatementGeographicalAxis_EBCD9B79334A0AC8AC6877CD204AE963" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srt_SegmentGeographicalDomain_9591F428D37DAC78016F77CD204A112D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_EBCD9B79334A0AC8AC6877CD204AE963" xlink:to="loc_srt_SegmentGeographicalDomain_9591F428D37DAC78016F77CD204A112D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srt_SegmentGeographicalDomain_9591F428D37DAC78016F77CD204A112D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_EBCD9B79334A0AC8AC6877CD204AE963" xlink:to="loc_srt_SegmentGeographicalDomain_9591F428D37DAC78016F77CD204A112D" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/stpr/2018/stpr-2018-01-31.xsd#stpr_CO" xlink:label="loc_stpr_CO_AB6193A5BA17062D029877CD204B452E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_9591F428D37DAC78016F77CD204A112D" xlink:to="loc_stpr_CO_AB6193A5BA17062D029877CD204B452E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinanceLeaseRightOfUseAsset" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAsset_84BEDC0917CDB7116EFB77CD204B2104" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8F0A1E45B5B70A724C1877CD204BC9FA" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAsset_84BEDC0917CDB7116EFB77CD204B2104" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeasesRentExpenseMinimumRentals" xlink:label="loc_us-gaap_OperatingLeasesRentExpenseMinimumRentals_0639F33CFBA0BF174DD677CD204C60C0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8F0A1E45B5B70A724C1877CD204BC9FA" xlink:to="loc_us-gaap_OperatingLeasesRentExpenseMinimumRentals_0639F33CFBA0BF174DD677CD204C60C0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeasesRentExpenseSubleaseRentals1" xlink:label="loc_us-gaap_OperatingLeasesRentExpenseSubleaseRentals1_2FD8478A0905EF51716577CD204CCE59" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8F0A1E45B5B70A724C1877CD204BC9FA" xlink:to="loc_us-gaap_OperatingLeasesRentExpenseSubleaseRentals1_2FD8478A0905EF51716577CD204CCE59" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeasesIncomeStatementSubleaseRevenue" xlink:label="loc_us-gaap_OperatingLeasesIncomeStatementSubleaseRevenue_781F9845DB149D9893E477CD204C3801" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8F0A1E45B5B70A724C1877CD204BC9FA" xlink:to="loc_us-gaap_OperatingLeasesIncomeStatementSubleaseRevenue_781F9845DB149D9893E477CD204C3801" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/LeasesCashPaidDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/LeasesLeaseExpenseDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/LeasesLeasesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/LeasesMaturitiesOfOperatingAndFinancingLeaseLiabilitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/LeasesOperatingLeaseUnderAsc840Details" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/LeasesSupplementalBalanceSheetDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/LeasesWeightedAverageDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/NetIncomeLossPerCommonShare" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/NetIncomeLossPerCommonShareAntidilutiveSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_5FA602074765DAFA25A65FA7B63C614F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_EB7ADFA7745F4D82E8A15FA7B63B2F0E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_5FA602074765DAFA25A65FA7B63C614F" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_EB7ADFA7745F4D82E8A15FA7B63B2F0E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8041DB1E7228B17F2F495FA7B63BA65F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_EB7ADFA7745F4D82E8A15FA7B63B2F0E" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8041DB1E7228B17F2F495FA7B63BA65F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_66E2AB174CE6F340708B5FA7B63B8494_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8041DB1E7228B17F2F495FA7B63BA65F" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_66E2AB174CE6F340708B5FA7B63B8494_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_66E2AB174CE6F340708B5FA7B63B8494" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8041DB1E7228B17F2F495FA7B63BA65F" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_66E2AB174CE6F340708B5FA7B63B8494" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_StockOptionsAndStockAwardsMember" xlink:label="loc_ktos_StockOptionsAndStockAwardsMember_FBDA210FED87E55B587C5FA7B63C0C40" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_66E2AB174CE6F340708B5FA7B63B8494" xlink:to="loc_ktos_StockOptionsAndStockAwardsMember_FBDA210FED87E55B587C5FA7B63C0C40" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_46DC8CA4F70C85FA8DCC5FA7B63C5EF4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_5FA602074765DAFA25A65FA7B63C614F" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_46DC8CA4F70C85FA8DCC5FA7B63C5EF4" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/NetIncomeLossPerCommonShareTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesContractAssetsAndLiabilitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesDetails" xlink:type="extended">
    <link:loc xlink:href="ktos-20191229.xsd#ktos_SignificantAccountingPoliciesDisclosureLineItems" xlink:label="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:type="locator" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_SignificantAccountingPoliciesDisclosureTable" xlink:label="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:to="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_B9D964BB02C5D41730F977CD221EE322" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:to="loc_us-gaap_AwardTypeAxis_B9D964BB02C5D41730F977CD221EE322" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_655E7E79DAD17C82EDE677CD221F91A0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_B9D964BB02C5D41730F977CD221EE322" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_655E7E79DAD17C82EDE677CD221F91A0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_655E7E79DAD17C82EDE677CD221F91A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_B9D964BB02C5D41730F977CD221EE322" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_655E7E79DAD17C82EDE677CD221F91A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_C07A4D9005B870F734E277CD221FC69B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_655E7E79DAD17C82EDE677CD221F91A0" xlink:to="loc_us-gaap_EmployeeStockOptionMember_C07A4D9005B870F734E277CD221FC69B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_A07A5CFC02FF81725D3D77CD2220FF76" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_A07A5CFC02FF81725D3D77CD2220FF76" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_996A4A6D8CE52A25BB4D77CD222049AE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_A07A5CFC02FF81725D3D77CD2220FF76" xlink:to="loc_us-gaap_SegmentDomain_996A4A6D8CE52A25BB4D77CD222049AE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_996A4A6D8CE52A25BB4D77CD222049AE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_A07A5CFC02FF81725D3D77CD2220FF76" xlink:to="loc_us-gaap_SegmentDomain_996A4A6D8CE52A25BB4D77CD222049AE" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_KratosGovernmentSolutionsMember" xlink:label="loc_ktos_KratosGovernmentSolutionsMember_0890073A1E23AB3D68F077CD22208439" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_996A4A6D8CE52A25BB4D77CD222049AE" xlink:to="loc_ktos_KratosGovernmentSolutionsMember_0890073A1E23AB3D68F077CD22208439" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_12EC8E03CE2678F54D8B77CD22208BF7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_12EC8E03CE2678F54D8B77CD22208BF7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_FA722266997CB0AF73B677CD2221F980_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_12EC8E03CE2678F54D8B77CD22208BF7" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_FA722266997CB0AF73B677CD2221F980_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_FA722266997CB0AF73B677CD2221F980" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_12EC8E03CE2678F54D8B77CD22208BF7" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_FA722266997CB0AF73B677CD2221F980" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentContinuingOperationsMember" xlink:label="loc_us-gaap_SegmentContinuingOperationsMember_4E84B445329914FFF69A77CD2221E980" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_FA722266997CB0AF73B677CD2221F980" xlink:to="loc_us-gaap_SegmentContinuingOperationsMember_4E84B445329914FFF69A77CD2221E980" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_AA20910C66FE1E1D8A5577CD2222409F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentContinuingOperationsMember_4E84B445329914FFF69A77CD2221E980" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_AA20910C66FE1E1D8A5577CD2222409F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_F2F1A962D63A4D59F32F77CD222216BF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_F2F1A962D63A4D59F32F77CD222216BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_45CA49CAF95749CC192B77CD2222FD8F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_F2F1A962D63A4D59F32F77CD222216BF" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_45CA49CAF95749CC192B77CD2222FD8F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_45CA49CAF95749CC192B77CD2222FD8F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_F2F1A962D63A4D59F32F77CD222216BF" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_45CA49CAF95749CC192B77CD2222FD8F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AllowanceForCreditLossMember" xlink:label="loc_us-gaap_AllowanceForCreditLossMember_2BDC3B912E4FB0EB390C77CD22225DCB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_45CA49CAF95749CC192B77CD2222FD8F" xlink:to="loc_us-gaap_AllowanceForCreditLossMember_2BDC3B912E4FB0EB390C77CD22225DCB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_25B1E2CBFC702C3ABC2377CD2223E2D2" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_25B1E2CBFC702C3ABC2377CD2223E2D2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0DB6BB52B60AF624218277CD22238B49_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_25B1E2CBFC702C3ABC2377CD2223E2D2" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0DB6BB52B60AF624218277CD22238B49_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0DB6BB52B60AF624218277CD22238B49" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_25B1E2CBFC702C3ABC2377CD2223E2D2" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0DB6BB52B60AF624218277CD22238B49" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BuildingAndBuildingImprovementsMember" xlink:label="loc_us-gaap_BuildingAndBuildingImprovementsMember_E4BB13F77DCFA1272B2277CD2223D901" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0DB6BB52B60AF624218277CD22238B49" xlink:to="loc_us-gaap_BuildingAndBuildingImprovementsMember_E4BB13F77DCFA1272B2277CD2223D901" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherMachineryAndEquipmentMember" xlink:label="loc_us-gaap_OtherMachineryAndEquipmentMember_A8F2BDB4038FDF2973BF77CD2224E9AC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0DB6BB52B60AF624218277CD22238B49" xlink:to="loc_us-gaap_OtherMachineryAndEquipmentMember_A8F2BDB4038FDF2973BF77CD2224E9AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComputerEquipmentMember" xlink:label="loc_us-gaap_ComputerEquipmentMember_C09AD27EDDB576DE65CA77CD22245774" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0DB6BB52B60AF624218277CD22238B49" xlink:to="loc_us-gaap_ComputerEquipmentMember_C09AD27EDDB576DE65CA77CD22245774" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_VehiclesFurnitureAndOfficeEquipmentMember" xlink:label="loc_ktos_VehiclesFurnitureAndOfficeEquipmentMember_1B6C37B609B951AB1DE477CD2224CD18" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0DB6BB52B60AF624218277CD22238B49" xlink:to="loc_ktos_VehiclesFurnitureAndOfficeEquipmentMember_1B6C37B609B951AB1DE477CD2224CD18" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_DCEA1E56FB7361E5A1CE77CD2224E4FF" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:to="loc_srt_RangeAxis_DCEA1E56FB7361E5A1CE77CD2224E4FF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_D5D23DAA0A984E55E07C77CD222434ED_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_DCEA1E56FB7361E5A1CE77CD2224E4FF" xlink:to="loc_srt_RangeMember_D5D23DAA0A984E55E07C77CD222434ED_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_D5D23DAA0A984E55E07C77CD222434ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_DCEA1E56FB7361E5A1CE77CD2224E4FF" xlink:to="loc_srt_RangeMember_D5D23DAA0A984E55E07C77CD222434ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_D8CE4DB98A6EE140FA4177CD222506FC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_D5D23DAA0A984E55E07C77CD222434ED" xlink:to="loc_srt_MinimumMember_D8CE4DB98A6EE140FA4177CD222506FC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_5C624F4550B91857651F77CD2225E07B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_D5D23DAA0A984E55E07C77CD222434ED" xlink:to="loc_srt_MaximumMember_5C624F4550B91857651F77CD2225E07B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementAxis" xlink:label="loc_srt_RestatementAxis_67A6C565791B9D2412E577CD22265657" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:to="loc_srt_RestatementAxis_67A6C565791B9D2412E577CD22265657" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementDomain" xlink:label="loc_srt_RestatementDomain_E6A3C29191D0019017FA77CD2226A0D6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_67A6C565791B9D2412E577CD22265657" xlink:to="loc_srt_RestatementDomain_E6A3C29191D0019017FA77CD2226A0D6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementDomain" xlink:label="loc_srt_RestatementDomain_E6A3C29191D0019017FA77CD2226A0D6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_67A6C565791B9D2412E577CD22265657" xlink:to="loc_srt_RestatementDomain_E6A3C29191D0019017FA77CD2226A0D6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementAdjustmentMember" xlink:label="loc_srt_RestatementAdjustmentMember_DEDA28768777CE5EB8C077CD2226C6D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_E6A3C29191D0019017FA77CD2226A0D6" xlink:to="loc_srt_RestatementAdjustmentMember_DEDA28768777CE5EB8C077CD2226C6D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_431C86C4C3642CDD277577CD2226BEB6" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_431C86C4C3642CDD277577CD2226BEB6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_326BB606EB62835CBAB777CD2227CA29_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_431C86C4C3642CDD277577CD2226BEB6" xlink:to="loc_us-gaap_TypeOfAdoptionMember_326BB606EB62835CBAB777CD2227CA29_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_326BB606EB62835CBAB777CD2227CA29" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_431C86C4C3642CDD277577CD2226BEB6" xlink:to="loc_us-gaap_TypeOfAdoptionMember_326BB606EB62835CBAB777CD2227CA29" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountingStandardsUpdate201409Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201409Member_FBFAE51D9854084815AB77CD2227977B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_326BB606EB62835CBAB777CD2227CA29" xlink:to="loc_us-gaap_AccountingStandardsUpdate201409Member_FBFAE51D9854084815AB77CD2227977B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_D39B90E5D6D581F8159277CD2228470F" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureTable_A2086C6BCC0C98C3CF7777CD221E0F78" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_D39B90E5D6D581F8159277CD2228470F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_DC9AF045ED0D06C353EC77CD2228EF2A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_D39B90E5D6D581F8159277CD2228470F" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_DC9AF045ED0D06C353EC77CD2228EF2A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_DC9AF045ED0D06C353EC77CD2228EF2A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_D39B90E5D6D581F8159277CD2228470F" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_DC9AF045ED0D06C353EC77CD2228EF2A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_54EBCF7D363F780EB4E477CD2228846F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_DC9AF045ED0D06C353EC77CD2228EF2A" xlink:to="loc_us-gaap_SubsequentEventMember_54EBCF7D363F780EB4E477CD2228846F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_3353A54FD336AB69682877CD2229B4C9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_3353A54FD336AB69682877CD2229B4C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NumberOfReportableSegments" xlink:label="loc_us-gaap_NumberOfReportableSegments_20EAEAFEB88591C1268277CD2229A3E2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:to="loc_us-gaap_NumberOfReportableSegments_20EAEAFEB88591C1268277CD2229A3E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract" xlink:label="loc_us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract_E8E62C621609E5BFD09777CD22299F1B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:to="loc_us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract_E8E62C621609E5BFD09777CD22299F1B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_5F403D107E3DC1FE861577CD222A36D5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract_E8E62C621609E5BFD09777CD22299F1B" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_5F403D107E3DC1FE861577CD222A36D5" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_EmployeeStockPurchasePlanOfferingPeriod" xlink:label="loc_ktos_EmployeeStockPurchasePlanOfferingPeriod_4767D759D56C044BE37677CD222AE7DB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract_E8E62C621609E5BFD09777CD22299F1B" xlink:to="loc_ktos_EmployeeStockPurchasePlanOfferingPeriod_4767D759D56C044BE37677CD222AE7DB" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_DeferredTaxBenefitfromStockOptionsExercised" xlink:label="loc_ktos_DeferredTaxBenefitfromStockOptionsExercised_C2B759A7553E834FEA8E77FD542F624C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract_E8E62C621609E5BFD09777CD22299F1B" xlink:to="loc_ktos_DeferredTaxBenefitfromStockOptionsExercised_C2B759A7553E834FEA8E77FD542F624C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_8CE75C8A86B580FB968577CD222A0E60" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract_E8E62C621609E5BFD09777CD22299F1B" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_8CE75C8A86B580FB968577CD222A0E60" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_3A279DD9C1E54D0903D877CD222ABB7C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_3A279DD9C1E54D0903D877CD222ABB7C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_F847332FA5234B70C89477CD222BF5CD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_3A279DD9C1E54D0903D877CD222ABB7C" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_F847332FA5234B70C89477CD222BF5CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProvisionForDoubtfulAccounts" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_837F634A76A2EA9398A577CD222B9DDC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_3A279DD9C1E54D0903D877CD222ABB7C" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_837F634A76A2EA9398A577CD222B9DDC" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_AllowanceForDoubtfulAccountsReceivableChargeOffsAndRecoveriesNet" xlink:label="loc_ktos_AllowanceForDoubtfulAccountsReceivableChargeOffsAndRecoveriesNet_E01C480D20E842A418A977CD222BBCBB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_3A279DD9C1E54D0903D877CD222ABB7C" xlink:to="loc_ktos_AllowanceForDoubtfulAccountsReceivableChargeOffsAndRecoveriesNet_E01C480D20E842A418A977CD222BBCBB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashAndCashEquivalentsAbstract" xlink:label="loc_us-gaap_CashAndCashEquivalentsAbstract_3C4ED538BAA610EE7F9E77CD222C28B2" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:to="loc_us-gaap_CashAndCashEquivalentsAbstract_3C4ED538BAA610EE7F9E77CD222C28B2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_3E63C424EC6DD225989077CD222CC3B7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAbstract_3C4ED538BAA610EE7F9E77CD222C28B2" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_3E63C424EC6DD225989077CD222CC3B7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAbstract" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAbstract_F9F8E181F090396D74E577CD222C5D4D" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAbstract_F9F8E181F090396D74E577CD222C5D4D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_D8F1B2050B088A6A98E377CD222C1568" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentAbstract_F9F8E181F090396D74E577CD222C5D4D" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_D8F1B2050B088A6A98E377CD222C1568" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestIncomeExpenseNetAbstract" xlink:label="loc_us-gaap_InterestIncomeExpenseNetAbstract_7207F8328B010DB1680877CD222D6BCD" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:to="loc_us-gaap_InterestIncomeExpenseNetAbstract_7207F8328B010DB1680877CD222D6BCD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpenseDebt" xlink:label="loc_us-gaap_InterestExpenseDebt_D13C4BCF2BD4E8B998AF77CD222D25C1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestIncomeExpenseNetAbstract_7207F8328B010DB1680877CD222D6BCD" xlink:to="loc_us-gaap_InterestExpenseDebt_D13C4BCF2BD4E8B998AF77CD222D25C1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestIncomeOther" xlink:label="loc_us-gaap_InterestIncomeOther_F605B8A7D72DDA430A2677CD222E542F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestIncomeExpenseNetAbstract_7207F8328B010DB1680877CD222D6BCD" xlink:to="loc_us-gaap_InterestIncomeOther_F605B8A7D72DDA430A2677CD222E542F" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_InterestExpenseIncomeNet" xlink:label="loc_ktos_InterestExpenseIncomeNet_8C03F8D714E4808D457777CD222E11FD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestIncomeExpenseNetAbstract_7207F8328B010DB1680877CD222D6BCD" xlink:to="loc_ktos_InterestExpenseIncomeNet_8C03F8D714E4808D457777CD222E11FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignCurrencyAbstract" xlink:label="loc_us-gaap_ForeignCurrencyAbstract_89873D70A3E261AA12DA77CD222E2F28" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:to="loc_us-gaap_ForeignCurrencyAbstract_89873D70A3E261AA12DA77CD222E2F28" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_F9E672036BDF901DD16C77CD222E1F01" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ForeignCurrencyAbstract_89873D70A3E261AA12DA77CD222E2F28" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_F9E672036BDF901DD16C77CD222E1F01" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstract" xlink:label="loc_us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstract_CEA384CDB50D6C8F4FD777CD222E796D" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_SignificantAccountingPoliciesDisclosureLineItems_D6D38BED2439A74211D077CD2228BEC4" xlink:to="loc_us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstract_CEA384CDB50D6C8F4FD777CD222E796D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_517AFF82D18B606AC9A777CD222F0699" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstract_CEA384CDB50D6C8F4FD777CD222E796D" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_517AFF82D18B606AC9A777CD222F0699" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseLiability" xlink:label="loc_us-gaap_OperatingLeaseLiability_BACFDCEB922EEF4FD63E77CD222F8425" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstract_CEA384CDB50D6C8F4FD777CD222E796D" xlink:to="loc_us-gaap_OperatingLeaseLiability_BACFDCEB922EEF4FD63E77CD222F8425" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_2E18801EFBC65D2545B277CD222F3D9A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstract_CEA384CDB50D6C8F4FD777CD222E796D" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_2E18801EFBC65D2545B277CD222F3D9A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesDisaggregationOfRevenueDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_30D1504D7CB91AE97228EEF28053CB47" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_FCA3DF0CECD3EF7EFA2BEEF280500098" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_30D1504D7CB91AE97228EEF28053CB47" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_FCA3DF0CECD3EF7EFA2BEEF280500098" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_D2F66B1910E179F5ADE8EEF28050D7AC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_FCA3DF0CECD3EF7EFA2BEEF280500098" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_D2F66B1910E179F5ADE8EEF28050D7AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_47953076393F8E8B89D3EEF28050EB60_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_D2F66B1910E179F5ADE8EEF28050D7AC" xlink:to="loc_us-gaap_SegmentDomain_47953076393F8E8B89D3EEF28050EB60_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_47953076393F8E8B89D3EEF28050EB60" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_D2F66B1910E179F5ADE8EEF28050D7AC" xlink:to="loc_us-gaap_SegmentDomain_47953076393F8E8B89D3EEF28050EB60" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_KratosGovernmentSolutionsMember" xlink:label="loc_ktos_KratosGovernmentSolutionsMember_6BF38F528BF19BE3C40CEEF28050FC05" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_47953076393F8E8B89D3EEF28050EB60" xlink:to="loc_ktos_KratosGovernmentSolutionsMember_6BF38F528BF19BE3C40CEEF28050FC05" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_KratosUnmannedSystemsMember" xlink:label="loc_ktos_KratosUnmannedSystemsMember_14FAE57350ECDEFF5D9AEEF28051EE2E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_47953076393F8E8B89D3EEF28050EB60" xlink:to="loc_ktos_KratosUnmannedSystemsMember_14FAE57350ECDEFF5D9AEEF28051EE2E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ContractWithCustomerBasisOfPricingAxis" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_4DCE8784A6CD4D7F8991EEF28051150B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_FCA3DF0CECD3EF7EFA2BEEF280500098" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_4DCE8784A6CD4D7F8991EEF28051150B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ContractWithCustomerBasisOfPricingDomain" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_EB87FA75DB174818BB86EEF280514C51_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_4DCE8784A6CD4D7F8991EEF28051150B" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_EB87FA75DB174818BB86EEF280514C51_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ContractWithCustomerBasisOfPricingDomain" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_EB87FA75DB174818BB86EEF280514C51" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_4DCE8784A6CD4D7F8991EEF28051150B" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_EB87FA75DB174818BB86EEF280514C51" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FixedPriceContractMember" xlink:label="loc_us-gaap_FixedPriceContractMember_9ECE00A35047EC1FFD78EEF280515708" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_EB87FA75DB174818BB86EEF280514C51" xlink:to="loc_us-gaap_FixedPriceContractMember_9ECE00A35047EC1FFD78EEF280515708" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_CostPlusFeeContractMember" xlink:label="loc_ktos_CostPlusFeeContractMember_13F077ABAB58D0A9337DEEF28051A735" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_EB87FA75DB174818BB86EEF280514C51" xlink:to="loc_ktos_CostPlusFeeContractMember_13F077ABAB58D0A9337DEEF28051A735" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TimeAndMaterialsContractMember" xlink:label="loc_us-gaap_TimeAndMaterialsContractMember_359306F1941BD27C53EFEEF2805243D6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_EB87FA75DB174818BB86EEF280514C51" xlink:to="loc_us-gaap_TimeAndMaterialsContractMember_359306F1941BD27C53EFEEF2805243D6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MajorCustomersAxis" xlink:label="loc_srt_MajorCustomersAxis_D588D63868F8CF3A4595EEF28052EA00" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_FCA3DF0CECD3EF7EFA2BEEF280500098" xlink:to="loc_srt_MajorCustomersAxis_D588D63868F8CF3A4595EEF28052EA00" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_NameOfMajorCustomerDomain" xlink:label="loc_srt_NameOfMajorCustomerDomain_BDDADDCFE82B786A5D75EEF280527A61_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_D588D63868F8CF3A4595EEF28052EA00" xlink:to="loc_srt_NameOfMajorCustomerDomain_BDDADDCFE82B786A5D75EEF280527A61_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_NameOfMajorCustomerDomain" xlink:label="loc_srt_NameOfMajorCustomerDomain_BDDADDCFE82B786A5D75EEF280527A61" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_D588D63868F8CF3A4595EEF28052EA00" xlink:to="loc_srt_NameOfMajorCustomerDomain_BDDADDCFE82B786A5D75EEF280527A61" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_UnitedStatesGovernmentMember" xlink:label="loc_ktos_UnitedStatesGovernmentMember_564C881902D0F01A0FFEEEF28052A762" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_BDDADDCFE82B786A5D75EEF280527A61" xlink:to="loc_ktos_UnitedStatesGovernmentMember_564C881902D0F01A0FFEEEF28052A762" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_NonUSGovernmentMember" xlink:label="loc_ktos_NonUSGovernmentMember_D0F97230EDBA68CE3911EEF28052382B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_BDDADDCFE82B786A5D75EEF280527A61" xlink:to="loc_ktos_NonUSGovernmentMember_D0F97230EDBA68CE3911EEF28052382B" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_UnitedStatesCommercialAndOtherCustomersMember" xlink:label="loc_ktos_UnitedStatesCommercialAndOtherCustomersMember_DB82E670F4C12944D3EBEEF280538526" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_BDDADDCFE82B786A5D75EEF280527A61" xlink:to="loc_ktos_UnitedStatesCommercialAndOtherCustomersMember_DB82E670F4C12944D3EBEEF280538526" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_A61314B141559D28A411EEF2805392FE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_30D1504D7CB91AE97228EEF28053CB47" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_A61314B141559D28A411EEF2805392FE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesRemainingPerformanceObligationsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_18DBBDD354B28D6E48E1EBB2862DB25F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_4E1925D2F70526CB5790EBB2862C732A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_18DBBDD354B28D6E48E1EBB2862DB25F" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_4E1925D2F70526CB5790EBB2862C732A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_B107343CB0C69D202025EBB2862DE43B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_4E1925D2F70526CB5790EBB2862C732A" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_B107343CB0C69D202025EBB2862DE43B" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercentage" xlink:label="loc_ktos_RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercentage_E1201B00BEF2454F0EB2EBB2862D3158" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_18DBBDD354B28D6E48E1EBB2862DB25F" xlink:to="loc_ktos_RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercentage_E1201B00BEF2454F0EB2EBB2862D3158" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesRevenueRecognitionNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_5A2BAB01BB6B05C44E99653FDA90B098" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_5A2BAB01BB6B05C44E99653FDA90B098" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementAxis" xlink:label="loc_srt_RestatementAxis_C909F5B13C857242248A653FDA90343D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_5A2BAB01BB6B05C44E99653FDA90B098" xlink:to="loc_srt_RestatementAxis_C909F5B13C857242248A653FDA90343D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementDomain" xlink:label="loc_srt_RestatementDomain_54191E0A7751B9D23672653FDA911125_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_C909F5B13C857242248A653FDA90343D" xlink:to="loc_srt_RestatementDomain_54191E0A7751B9D23672653FDA911125_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementDomain" xlink:label="loc_srt_RestatementDomain_54191E0A7751B9D23672653FDA911125" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_C909F5B13C857242248A653FDA90343D" xlink:to="loc_srt_RestatementDomain_54191E0A7751B9D23672653FDA911125" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementAdjustmentMember" xlink:label="loc_srt_RestatementAdjustmentMember_8879ADDDF9F530B8CBB3653FDA911620" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_54191E0A7751B9D23672653FDA911125" xlink:to="loc_srt_RestatementAdjustmentMember_8879ADDDF9F530B8CBB3653FDA911620" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_AC45F10D3D9FE10F147A653FDA91C31D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_5A2BAB01BB6B05C44E99653FDA90B098" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_AC45F10D3D9FE10F147A653FDA91C31D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_AE4EAA13DEDD5D671BD7653FDA9220EB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_AC45F10D3D9FE10F147A653FDA91C31D" xlink:to="loc_us-gaap_TypeOfAdoptionMember_AE4EAA13DEDD5D671BD7653FDA9220EB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_AE4EAA13DEDD5D671BD7653FDA9220EB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_AC45F10D3D9FE10F147A653FDA91C31D" xlink:to="loc_us-gaap_TypeOfAdoptionMember_AE4EAA13DEDD5D671BD7653FDA9220EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountingStandardsUpdate201409Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201409Member_0D801AFE3D77003CC1C2653FDA92A7C3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_AE4EAA13DEDD5D671BD7653FDA9220EB" xlink:to="loc_us-gaap_AccountingStandardsUpdate201409Member_0D801AFE3D77003CC1C2653FDA92A7C3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_D16FFDFAEAE94E54F20B653FDA926149" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_5A2BAB01BB6B05C44E99653FDA90B098" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_D16FFDFAEAE94E54F20B653FDA926149" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_CE7CFCFD390346953B1F653FDA925B45_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_D16FFDFAEAE94E54F20B653FDA926149" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_CE7CFCFD390346953B1F653FDA925B45_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_CE7CFCFD390346953B1F653FDA925B45" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_D16FFDFAEAE94E54F20B653FDA926149" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_CE7CFCFD390346953B1F653FDA925B45" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member" xlink:label="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_965C1A1E3A00CBF8F6D3653FDA9309F4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_CE7CFCFD390346953B1F653FDA925B45" xlink:to="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_965C1A1E3A00CBF8F6D3653FDA9309F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis_608900263C72C772D5E8653FDA93F671" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_5A2BAB01BB6B05C44E99653FDA90B098" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis_608900263C72C772D5E8653FDA93F671" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivablesBillingStatusDomain" xlink:label="loc_us-gaap_ReceivablesBillingStatusDomain_8E9A5AA50D8BB5C28586653FDA93913F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis_608900263C72C772D5E8653FDA93F671" xlink:to="loc_us-gaap_ReceivablesBillingStatusDomain_8E9A5AA50D8BB5C28586653FDA93913F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivablesBillingStatusDomain" xlink:label="loc_us-gaap_ReceivablesBillingStatusDomain_8E9A5AA50D8BB5C28586653FDA93913F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivablesByBillingStatusTypeAxis_608900263C72C772D5E8653FDA93F671" xlink:to="loc_us-gaap_ReceivablesBillingStatusDomain_8E9A5AA50D8BB5C28586653FDA93913F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnbilledRevenuesMember" xlink:label="loc_us-gaap_UnbilledRevenuesMember_147F8C152A63D29E514F653FDA93C443" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivablesBillingStatusDomain_8E9A5AA50D8BB5C28586653FDA93913F" xlink:to="loc_us-gaap_UnbilledRevenuesMember_147F8C152A63D29E514F653FDA93C443" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MajorCustomersAxis" xlink:label="loc_srt_MajorCustomersAxis_EFB88727C83D2545B442655759485144" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_5A2BAB01BB6B05C44E99653FDA90B098" xlink:to="loc_srt_MajorCustomersAxis_EFB88727C83D2545B442655759485144" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_NameOfMajorCustomerDomain" xlink:label="loc_srt_NameOfMajorCustomerDomain_BC9422C3310571B6B46D65575957701C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_EFB88727C83D2545B442655759485144" xlink:to="loc_srt_NameOfMajorCustomerDomain_BC9422C3310571B6B46D65575957701C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_NameOfMajorCustomerDomain" xlink:label="loc_srt_NameOfMajorCustomerDomain_BC9422C3310571B6B46D65575957701C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_EFB88727C83D2545B442655759485144" xlink:to="loc_srt_NameOfMajorCustomerDomain_BC9422C3310571B6B46D65575957701C" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_TforCMember" xlink:label="loc_ktos_TforCMember_901ECF9ADE8434FAB2016557E43B3337" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_BC9422C3310571B6B46D65575957701C" xlink:to="loc_ktos_TforCMember_901ECF9ADE8434FAB2016557E43B3337" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_InternationalCustomerMember" xlink:label="loc_ktos_InternationalCustomerMember_8B2C084274E9D770F874655843BB7855" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_BC9422C3310571B6B46D65575957701C" xlink:to="loc_ktos_InternationalCustomerMember_8B2C084274E9D770F874655843BB7855" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_DE0697761F4B9FA7294D653FDA9428DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_DE0697761F4B9FA7294D653FDA9428DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_136D59A1EDD3918F0547653FDA94EF5E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_136D59A1EDD3918F0547653FDA94EF5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CostOfRevenue" xlink:label="loc_us-gaap_CostOfRevenue_64B8395C000F3446C5F5653FDA94DEA8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_us-gaap_CostOfRevenue_64B8395C000F3446C5F5653FDA94DEA8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_2E57A178B95523A0BB8C653FDA946A5A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_2E57A178B95523A0BB8C653FDA946A5A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProvisionForLossOnContracts" xlink:label="loc_us-gaap_ProvisionForLossOnContracts_2F2A3E46A121AE07014E653FDA94D7EE" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_us-gaap_ProvisionForLossOnContracts_2F2A3E46A121AE07014E653FDA94D7EE" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_ContractWithCustomerAssetIncreaseDecrease" xlink:label="loc_ktos_ContractWithCustomerAssetIncreaseDecrease_1805D450C9CF014D0F6F653FDA94772A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_ktos_ContractWithCustomerAssetIncreaseDecrease_1805D450C9CF014D0F6F653FDA94772A" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_ContractWithCustomerLiabilityIncreaseDecrease" xlink:label="loc_ktos_ContractWithCustomerLiabilityIncreaseDecrease_57BA2116C876A7793F48653FDA955537" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_ktos_ContractWithCustomerLiabilityIncreaseDecrease_57BA2116C876A7793F48653FDA955537" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_82656EE22B2A82519566653FDA954DD3" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_82656EE22B2A82519566653FDA954DD3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsReceivableGross" xlink:label="loc_us-gaap_AccountsReceivableGross_23DE5F1E851022F519D2653FDA9524BF" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_us-gaap_AccountsReceivableGross_23DE5F1E851022F519D2653FDA9524BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ContractWithCustomerAssetNet" xlink:label="loc_us-gaap_ContractWithCustomerAssetNet_3223ADDD6EE2E5BDC7C0655607F76B23" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F0122FD8463F53E0AE6C653FDA93A2BD" xlink:to="loc_us-gaap_ContractWithCustomerAssetNet_3223ADDD6EE2E5BDC7C0655607F76B23" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/OrganizationAndSummaryOfSignificantAccountingPoliciesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/QuarterlyFinancialDataUnaudited" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/QuarterlyFinancialDataUnauditedSummarizedQuarterlyFinancialInformationDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/QuarterlyFinancialDataUnauditedTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RedeemableNoncontrollingInterest" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RetirementPlans" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RetirementPlansDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SegmentInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SegmentInformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_1916D965FDCA5380B183F0E04BEBCD6F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8B265FA1D9A0B16A1B8BF0E04BE961DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1916D965FDCA5380B183F0E04BEBCD6F" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8B265FA1D9A0B16A1B8BF0E04BE961DA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementGeographicalAxis" xlink:label="loc_srt_StatementGeographicalAxis_3844C57E9A22CB5E9CA8F0E04BEAEBFC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8B265FA1D9A0B16A1B8BF0E04BE961DA" xlink:to="loc_srt_StatementGeographicalAxis_3844C57E9A22CB5E9CA8F0E04BEAEBFC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srt_SegmentGeographicalDomain_99476A426DD1D335BC51F0E04BEAA0E9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_3844C57E9A22CB5E9CA8F0E04BEAEBFC" xlink:to="loc_srt_SegmentGeographicalDomain_99476A426DD1D335BC51F0E04BEAA0E9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srt_SegmentGeographicalDomain_99476A426DD1D335BC51F0E04BEAA0E9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_3844C57E9A22CB5E9CA8F0E04BEAEBFC" xlink:to="loc_srt_SegmentGeographicalDomain_99476A426DD1D335BC51F0E04BEAA0E9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NonUsMember" xlink:label="loc_us-gaap_NonUsMember_60499A050850652A284EF0E04BEACE2D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_99476A426DD1D335BC51F0E04BEAA0E9" xlink:to="loc_us-gaap_NonUsMember_60499A050850652A284EF0E04BEACE2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_5A655CDA6493572D539FF0E04BEA17A3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8B265FA1D9A0B16A1B8BF0E04BE961DA" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_5A655CDA6493572D539FF0E04BEA17A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_142B97EDF0FAFE74ED71F0E04BEA06B9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_5A655CDA6493572D539FF0E04BEA17A3" xlink:to="loc_us-gaap_SegmentDomain_142B97EDF0FAFE74ED71F0E04BEA06B9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_142B97EDF0FAFE74ED71F0E04BEA06B9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_5A655CDA6493572D539FF0E04BEA17A3" xlink:to="loc_us-gaap_SegmentDomain_142B97EDF0FAFE74ED71F0E04BEA06B9" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_KratosUnmannedSystemsMember" xlink:label="loc_ktos_KratosUnmannedSystemsMember_9D48B0F53E7ED35DF67DF0E04BEBCB7E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_142B97EDF0FAFE74ED71F0E04BEA06B9" xlink:to="loc_ktos_KratosUnmannedSystemsMember_9D48B0F53E7ED35DF67DF0E04BEBCB7E" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_KratosGovernmentSolutionsMember" xlink:label="loc_ktos_KratosGovernmentSolutionsMember_82241D31DA076960A0EEF0E04BEBA9FA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_142B97EDF0FAFE74ED71F0E04BEA06B9" xlink:to="loc_ktos_KratosGovernmentSolutionsMember_82241D31DA076960A0EEF0E04BEBA9FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NumberOfReportableSegments" xlink:label="loc_us-gaap_NumberOfReportableSegments_10DAB5EDD7ABD62D1B61F0E04BEBC31B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1916D965FDCA5380B183F0E04BEBCD6F" xlink:to="loc_us-gaap_NumberOfReportableSegments_10DAB5EDD7ABD62D1B61F0E04BEBC31B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_1911E1736022F76939A1F0E04BEC5E03" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1916D965FDCA5380B183F0E04BEBCD6F" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_1911E1736022F76939A1F0E04BEC5E03" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_EntityWideDisclosureOnGeographicAreasRevenueFromExternalCustomersAttributedToForeignCountriesPercentage" xlink:label="loc_ktos_EntityWideDisclosureOnGeographicAreasRevenueFromExternalCustomersAttributedToForeignCountriesPercentage_CA6D1313B5184AD74F91F0E04BEC7B2E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1916D965FDCA5380B183F0E04BEBCD6F" xlink:to="loc_ktos_EntityWideDisclosureOnGeographicAreasRevenueFromExternalCustomersAttributedToForeignCountriesPercentage_CA6D1313B5184AD74F91F0E04BEC7B2E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillImpairmentLoss" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_158E4E3342C2BB7D3601F0E04BECAD50" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1916D965FDCA5380B183F0E04BEBCD6F" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_158E4E3342C2BB7D3601F0E04BECAD50" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_EntityWideDisclosureOnGeographicAreasAssetsInForeignCountries" xlink:label="loc_ktos_EntityWideDisclosureOnGeographicAreasAssetsInForeignCountries_83CC510E84FC441B89ADF0E04BECCCEC" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1916D965FDCA5380B183F0E04BEBCD6F" xlink:to="loc_ktos_EntityWideDisclosureOnGeographicAreasAssetsInForeignCountries_83CC510E84FC441B89ADF0E04BECCCEC" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SegmentInformationRevenuesOperatingIncomeLossAndAssetsByReportableSegmentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_26C237F964A3CB25FE345A392F446A37" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_50570A247B33A4B294085A392F3B5274" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_26C237F964A3CB25FE345A392F446A37" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_50570A247B33A4B294085A392F3B5274" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srt_ProductOrServiceAxis_DAD3F15A7A28978511B85A392F3BCB07" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_50570A247B33A4B294085A392F3B5274" xlink:to="loc_srt_ProductOrServiceAxis_DAD3F15A7A28978511B85A392F3BCB07" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_2AED0E6DE82AD83AF58C5A392F3CA3F1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_DAD3F15A7A28978511B85A392F3BCB07" xlink:to="loc_srt_ProductsAndServicesDomain_2AED0E6DE82AD83AF58C5A392F3CA3F1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_2AED0E6DE82AD83AF58C5A392F3CA3F1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_DAD3F15A7A28978511B85A392F3BCB07" xlink:to="loc_srt_ProductsAndServicesDomain_2AED0E6DE82AD83AF58C5A392F3CA3F1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ServiceMember" xlink:label="loc_us-gaap_ServiceMember_C24BCF0D92E600C0826B5A392F3C5BCD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_2AED0E6DE82AD83AF58C5A392F3CA3F1" xlink:to="loc_us-gaap_ServiceMember_C24BCF0D92E600C0826B5A392F3C5BCD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProductMember" xlink:label="loc_us-gaap_ProductMember_7784CFD0D8137F25735A5A392F3C1522" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_2AED0E6DE82AD83AF58C5A392F3CA3F1" xlink:to="loc_us-gaap_ProductMember_7784CFD0D8137F25735A5A392F3C1522" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="loc_srt_ConsolidationItemsAxis_1CD641FC14428421E4E65A392F3CE3EB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_50570A247B33A4B294085A392F3B5274" xlink:to="loc_srt_ConsolidationItemsAxis_1CD641FC14428421E4E65A392F3CE3EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_AE1DB3633134747E88DC5A392F3CB73F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_1CD641FC14428421E4E65A392F3CE3EB" xlink:to="loc_srt_ConsolidationItemsDomain_AE1DB3633134747E88DC5A392F3CB73F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_AE1DB3633134747E88DC5A392F3CB73F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_1CD641FC14428421E4E65A392F3CE3EB" xlink:to="loc_srt_ConsolidationItemsDomain_AE1DB3633134747E88DC5A392F3CB73F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="loc_us-gaap_OperatingSegmentsMember_EECF464FC4B0A3E255AB5A392F3DCAE5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_AE1DB3633134747E88DC5A392F3CB73F" xlink:to="loc_us-gaap_OperatingSegmentsMember_EECF464FC4B0A3E255AB5A392F3DCAE5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MaterialReconcilingItemsMember" xlink:label="loc_us-gaap_MaterialReconcilingItemsMember_0593D1E4FB90BE5DF6125A392F3DC065" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_AE1DB3633134747E88DC5A392F3CB73F" xlink:to="loc_us-gaap_MaterialReconcilingItemsMember_0593D1E4FB90BE5DF6125A392F3DC065" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_CC7C28619B3EF4577FE35A392F3D379C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_50570A247B33A4B294085A392F3B5274" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_CC7C28619B3EF4577FE35A392F3D379C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_C4791F991EB6863BC6915A392F3DEE51_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_CC7C28619B3EF4577FE35A392F3D379C" xlink:to="loc_us-gaap_SegmentDomain_C4791F991EB6863BC6915A392F3DEE51_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_C4791F991EB6863BC6915A392F3DEE51" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_CC7C28619B3EF4577FE35A392F3D379C" xlink:to="loc_us-gaap_SegmentDomain_C4791F991EB6863BC6915A392F3DEE51" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_KratosGovernmentSolutionsMember" xlink:label="loc_ktos_KratosGovernmentSolutionsMember_51A010669F8D8F4411505A392F3E992D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_C4791F991EB6863BC6915A392F3DEE51" xlink:to="loc_ktos_KratosGovernmentSolutionsMember_51A010669F8D8F4411505A392F3E992D" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_KratosUnmannedSystemsMember" xlink:label="loc_ktos_KratosUnmannedSystemsMember_D6C76E7E287D13C17DAC5A392F4249BD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_C4791F991EB6863BC6915A392F3DEE51" xlink:to="loc_ktos_KratosUnmannedSystemsMember_D6C76E7E287D13C17DAC5A392F4249BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementOperatingActivitiesSegmentAxis" xlink:label="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_E59F8928971056F0D9515A392F428CC2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_50570A247B33A4B294085A392F3B5274" xlink:to="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_E59F8928971056F0D9515A392F428CC2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentOperatingActivitiesDomain" xlink:label="loc_us-gaap_SegmentOperatingActivitiesDomain_E72A1C921A8EF3165EFA5A392F422B43_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_E59F8928971056F0D9515A392F428CC2" xlink:to="loc_us-gaap_SegmentOperatingActivitiesDomain_E72A1C921A8EF3165EFA5A392F422B43_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentOperatingActivitiesDomain" xlink:label="loc_us-gaap_SegmentOperatingActivitiesDomain_E72A1C921A8EF3165EFA5A392F422B43" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_E59F8928971056F0D9515A392F428CC2" xlink:to="loc_us-gaap_SegmentOperatingActivitiesDomain_E72A1C921A8EF3165EFA5A392F422B43" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDiscontinuedOperationsMember" xlink:label="loc_us-gaap_SegmentDiscontinuedOperationsMember_CCAB565A70EF9FF274A75A392F44E21C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentOperatingActivitiesDomain_E72A1C921A8EF3165EFA5A392F422B43" xlink:to="loc_us-gaap_SegmentDiscontinuedOperationsMember_CCAB565A70EF9FF274A75A392F44E21C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_B1EB8162209709E6BD895A392F44A015" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_26C237F964A3CB25FE345A392F446A37" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_B1EB8162209709E6BD895A392F44A015" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_0AE0C40870BDB6B7AE4B5A392F44AE8C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_26C237F964A3CB25FE345A392F446A37" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_0AE0C40870BDB6B7AE4B5A392F44AE8C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_9AC658B0C40FD3B822035A392F45B23F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_26C237F964A3CB25FE345A392F446A37" xlink:to="loc_us-gaap_OperatingIncomeLoss_9AC658B0C40FD3B822035A392F45B23F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaap_Assets_D32A83636D1130E29A365A392F458F58" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_26C237F964A3CB25FE345A392F446A37" xlink:to="loc_us-gaap_Assets_D32A83636D1130E29A365A392F458F58" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SegmentInformationTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SignificantCustomers" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SignificantCustomersDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:label="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_1BFDA1538D17DAB77569EBB28613ECD1" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable" xlink:label="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_FDF07352C3772271D1E2EBB28611E43F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_1BFDA1538D17DAB77569EBB28613ECD1" xlink:to="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_FDF07352C3772271D1E2EBB28611E43F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MajorCustomersAxis" xlink:label="loc_srt_MajorCustomersAxis_BD2CD9B27FFBC673DD2AEBB286115852" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_FDF07352C3772271D1E2EBB28611E43F" xlink:to="loc_srt_MajorCustomersAxis_BD2CD9B27FFBC673DD2AEBB286115852" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_NameOfMajorCustomerDomain" xlink:label="loc_srt_NameOfMajorCustomerDomain_FDF9E5421D04B1E30643EBB2861274FD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_BD2CD9B27FFBC673DD2AEBB286115852" xlink:to="loc_srt_NameOfMajorCustomerDomain_FDF9E5421D04B1E30643EBB2861274FD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_NameOfMajorCustomerDomain" xlink:label="loc_srt_NameOfMajorCustomerDomain_FDF9E5421D04B1E30643EBB2861274FD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_BD2CD9B27FFBC673DD2AEBB286115852" xlink:to="loc_srt_NameOfMajorCustomerDomain_FDF9E5421D04B1E30643EBB2861274FD" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_USGovernmentMember" xlink:label="loc_ktos_USGovernmentMember_3ED43E6C19D7A76C7647EBB2861244C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_FDF9E5421D04B1E30643EBB2861274FD" xlink:to="loc_ktos_USGovernmentMember_3ED43E6C19D7A76C7647EBB2861244C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_FA23871CDE8C9D99942AEBB28612CB1F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_FDF07352C3772271D1E2EBB28611E43F" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_FA23871CDE8C9D99942AEBB28612CB1F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_B76473A5BF5083B59291EBB2861269F1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_FA23871CDE8C9D99942AEBB28612CB1F" xlink:to="loc_us-gaap_SegmentDomain_B76473A5BF5083B59291EBB2861269F1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_B76473A5BF5083B59291EBB2861269F1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_FA23871CDE8C9D99942AEBB28612CB1F" xlink:to="loc_us-gaap_SegmentDomain_B76473A5BF5083B59291EBB2861269F1" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_KratosGovernmentSolutionsMember" xlink:label="loc_ktos_KratosGovernmentSolutionsMember_9AF556A22A940FE43616EBB28613835F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_B76473A5BF5083B59291EBB2861269F1" xlink:to="loc_ktos_KratosGovernmentSolutionsMember_9AF556A22A940FE43616EBB28613835F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_E4EE55B4BF24F5A1891FEBB286131642" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_1BFDA1538D17DAB77569EBB28613ECD1" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_E4EE55B4BF24F5A1891FEBB286131642" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_8DB820B268FBF7044BE5EBB28613D0E5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_1BFDA1538D17DAB77569EBB28613ECD1" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_8DB820B268FBF7044BE5EBB28613D0E5" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/StockholdersEquity" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/StockholdersEquityCommonStockDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_985F48E3FA098F295222653FD8639F0E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_5303B410271EC4ED2060653FD860ECA3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_985F48E3FA098F295222653FD8639F0E" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_5303B410271EC4ED2060653FD860ECA3" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_AF9778769B0090D00434653FD860C1BC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_5303B410271EC4ED2060653FD860ECA3" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_AF9778769B0090D00434653FD860C1BC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_BF72EF625281CACC6BA5653FD861C461_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_AF9778769B0090D00434653FD860C1BC" xlink:to="loc_us-gaap_EquityComponentDomain_BF72EF625281CACC6BA5653FD861C461_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_BF72EF625281CACC6BA5653FD861C461" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_AF9778769B0090D00434653FD860C1BC" xlink:to="loc_us-gaap_EquityComponentDomain_BF72EF625281CACC6BA5653FD861C461" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_192586AF0262CF5C7068653FD86175CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_BF72EF625281CACC6BA5653FD861C461" xlink:to="loc_us-gaap_CommonStockMember_192586AF0262CF5C7068653FD86175CA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_7E5045D79A032CE1FC3E653FD8612D0C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_5303B410271EC4ED2060653FD860ECA3" xlink:to="loc_us-gaap_DebtInstrumentAxis_7E5045D79A032CE1FC3E653FD8612D0C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9F38FFA01A34068330E3653FD8615292_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_7E5045D79A032CE1FC3E653FD8612D0C" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9F38FFA01A34068330E3653FD8615292_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9F38FFA01A34068330E3653FD8615292" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_7E5045D79A032CE1FC3E653FD8612D0C" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9F38FFA01A34068330E3653FD8615292" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_SevenPercentSeniorNotesDue2019Member" xlink:label="loc_ktos_SevenPercentSeniorNotesDue2019Member_7AD8E5E51F50882E0752653FD862C5DF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9F38FFA01A34068330E3653FD8615292" xlink:to="loc_ktos_SevenPercentSeniorNotesDue2019Member_7AD8E5E51F50882E0752653FD862C5DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_62C60A98F75AC421436B653FD862106D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_5303B410271EC4ED2060653FD860ECA3" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_62C60A98F75AC421436B653FD862106D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_B23BFB4A6DE6618DCB6B653FD8629BF8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_62C60A98F75AC421436B653FD862106D" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_B23BFB4A6DE6618DCB6B653FD8629BF8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_B23BFB4A6DE6618DCB6B653FD8629BF8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_62C60A98F75AC421436B653FD862106D" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_B23BFB4A6DE6618DCB6B653FD8629BF8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_570E273B70E22A691EC4653FD86244C7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_B23BFB4A6DE6618DCB6B653FD8629BF8" xlink:to="loc_us-gaap_SeniorNotesMember_570E273B70E22A691EC4653FD86244C7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_7D8DB053A988FDD89E34653FD8633948" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_985F48E3FA098F295222653FD8639F0E" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_7D8DB053A988FDD89E34653FD8633948" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SaleOfStockPricePerShare" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_E6145D79384018FFBE5E653FD868E6B1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_985F48E3FA098F295222653FD8639F0E" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_E6145D79384018FFBE5E653FD868E6B1" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_SaleofStockConsiderationReceivedonTransactionGross" xlink:label="loc_ktos_SaleofStockConsiderationReceivedonTransactionGross_6992E202B42B22438847653FD8680693" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_985F48E3FA098F295222653FD8639F0E" xlink:to="loc_ktos_SaleofStockConsiderationReceivedonTransactionGross_6992E202B42B22438847653FD8680693" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_3270DB247B669E66A209653FD86972C7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_985F48E3FA098F295222653FD8639F0E" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_3270DB247B669E66A209653FD86972C7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RepaymentsOfSecuredDebt" xlink:label="loc_us-gaap_RepaymentsOfSecuredDebt_2916538D6C7C0D82E5FD653FD8697C3E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_985F48E3FA098F295222653FD8639F0E" xlink:to="loc_us-gaap_RepaymentsOfSecuredDebt_2916538D6C7C0D82E5FD653FD8697C3E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_D98C8681B46C22999DB8653FD86968D7" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_985F48E3FA098F295222653FD8639F0E" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_D98C8681B46C22999DB8653FD86968D7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRepurchaseAmount" xlink:label="loc_us-gaap_DebtInstrumentRepurchaseAmount_BEDA9AEEF2A94E214553653FD8699827" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_985F48E3FA098F295222653FD8639F0E" xlink:to="loc_us-gaap_DebtInstrumentRepurchaseAmount_BEDA9AEEF2A94E214553653FD8699827" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/StockholdersEquityEmployeeStockPurchasePlanDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_34B46A880538A4C57015EBB28633CC57" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_34B46A880538A4C57015EBB28633CC57" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_E28BC4588ABAEE5216C8EBB286334AC6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_34B46A880538A4C57015EBB28633CC57" xlink:to="loc_us-gaap_AwardTypeAxis_E28BC4588ABAEE5216C8EBB286334AC6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3B70925C28C6914126E9EBB28633C4F6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_E28BC4588ABAEE5216C8EBB286334AC6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3B70925C28C6914126E9EBB28633C4F6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3B70925C28C6914126E9EBB28633C4F6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_E28BC4588ABAEE5216C8EBB286334AC6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3B70925C28C6914126E9EBB28633C4F6" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_EmployeeStockPurchasePlanMember" xlink:label="loc_ktos_EmployeeStockPurchasePlanMember_D7293BC4DA8E6B39E72CEBB28633649B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3B70925C28C6914126E9EBB28633C4F6" xlink:to="loc_ktos_EmployeeStockPurchasePlanMember_D7293BC4DA8E6B39E72CEBB28633649B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_B7A6DD867263FE642EA9EBB286341B3C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_B7A6DD867263FE642EA9EBB286341B3C" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAwardMinimumWeeklyEmployment" xlink:label="loc_ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAwardMinimumWeeklyEmployment_2B41BE2565746DACCCC7EBB286348E3B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAwardMinimumWeeklyEmployment_2B41BE2565746DACCCC7EBB286348E3B" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAwardMinimumAnnualEmployment" xlink:label="loc_ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAwardMinimumAnnualEmployment_B02D1E9DA9D5AF230940EBB28634B8C9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAwardMinimumAnnualEmployment_B02D1E9DA9D5AF230940EBB28634B8C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate_F2F8CD93310439C8B8A4EBB2863407F8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate_F2F8CD93310439C8B8A4EBB2863407F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_81FAC9E27AABDB3A747DEBB28635E2E0" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_81FAC9E27AABDB3A747DEBB28635E2E0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_05610AE2B19F3D62A63FEBB28635A78B" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_05610AE2B19F3D62A63FEBB28635A78B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_1DF4A04E322895AC76E6EBB286359F65" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_1DF4A04E322895AC76E6EBB286359F65" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_D274D8634D2E84625D95EBB28635C199" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_D274D8634D2E84625D95EBB28635C199" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased_1E6D1EFC7F3AA9C131B2EBB28635742F" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased_1E6D1EFC7F3AA9C131B2EBB28635742F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_F331A0145AA15E01B907EBB28635D3CB" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_99C2D3EC5F524E496CF8EBB2863467CD" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_F331A0145AA15E01B907EBB28635D3CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_0AE309EDE7A91EAED0D1EBB28636DFD1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_F331A0145AA15E01B907EBB28635D3CB" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_0AE309EDE7A91EAED0D1EBB28636DFD1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_A7BD091DA4125CC59357EBB28636CB74" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_F331A0145AA15E01B907EBB28635D3CB" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_A7BD091DA4125CC59357EBB28636CB74" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_0B210169010B053988C8EBB28636E053" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_F331A0145AA15E01B907EBB28635D3CB" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_0B210169010B053988C8EBB28636E053" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_7B1CFA62B44B8780A7B3EBB28636A0C8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_F331A0145AA15E01B907EBB28635D3CB" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_7B1CFA62B44B8780A7B3EBB28636A0C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_E9E5F1EB8BF9CA188755EBB286361B23" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_F331A0145AA15E01B907EBB28635D3CB" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_E9E5F1EB8BF9CA188755EBB286361B23" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_35A4DF29A2CF409E0779EBB286362924" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_F331A0145AA15E01B907EBB28635D3CB" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_35A4DF29A2CF409E0779EBB286362924" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_A14E536B45DC879D953CEBB286376BA6" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_F331A0145AA15E01B907EBB28635D3CB" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_A14E536B45DC879D953CEBB286376BA6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/StockholdersEquityGrantsAndExercisesUnderOptionPlansDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/StockholdersEquityRestrictedStockUnitActivityDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EA20262253DE8E1D909777CD1E2809F4" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_C2A0FAB9FEB33DBD788C77CD1E26C5CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EA20262253DE8E1D909777CD1E2809F4" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_C2A0FAB9FEB33DBD788C77CD1E26C5CA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_A5206183BB7F1141414477CD1E2636FE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_C2A0FAB9FEB33DBD788C77CD1E26C5CA" xlink:to="loc_us-gaap_AwardTypeAxis_A5206183BB7F1141414477CD1E2636FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_D9F9A26EC8BC989B239D77CD1E27A264_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_A5206183BB7F1141414477CD1E2636FE" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_D9F9A26EC8BC989B239D77CD1E27A264_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_D9F9A26EC8BC989B239D77CD1E27A264" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_A5206183BB7F1141414477CD1E2636FE" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_D9F9A26EC8BC989B239D77CD1E27A264" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_61FD4CA067CC97AE903877CD1E27C1F4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_D9F9A26EC8BC989B239D77CD1E27A264" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_61FD4CA067CC97AE903877CD1E27C1F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_36620F2B913281F99B7B77CD1E283195" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EA20262253DE8E1D909777CD1E2809F4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_36620F2B913281F99B7B77CD1E283195" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_76C311A0BECE9E79D01777CD1E282660" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_36620F2B913281F99B7B77CD1E283195" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_76C311A0BECE9E79D01777CD1E282660" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_67DF89CBC4CA9870DE3077CD1E28E3F0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_36620F2B913281F99B7B77CD1E283195" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_67DF89CBC4CA9870DE3077CD1E28E3F0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_2D61AADB3F5B398EF29F77CD1E29DFA3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_36620F2B913281F99B7B77CD1E283195" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_2D61AADB3F5B398EF29F77CD1E29DFA3" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsVestedButNotReleased" xlink:label="loc_ktos_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsVestedButNotReleased_222658BB45D7F178B9B477CD1E29F280" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_36620F2B913281F99B7B77CD1E283195" xlink:to="loc_ktos_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsVestedButNotReleased_222658BB45D7F178B9B477CD1E29F280" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01B8F48F25173589AE5277CD1E2A07C7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EA20262253DE8E1D909777CD1E2809F4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01B8F48F25173589AE5277CD1E2A07C7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_9758B85F19A786826E5A77CD1E2A8A49" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01B8F48F25173589AE5277CD1E2A07C7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_9758B85F19A786826E5A77CD1E2A8A49" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_1F090251E7601FC4300277CD1E2A54B5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01B8F48F25173589AE5277CD1E2A07C7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_1F090251E7601FC4300277CD1E2A54B5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_B1B2B3733C6C026FB32977CD1E2A5170" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01B8F48F25173589AE5277CD1E2A07C7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_B1B2B3733C6C026FB32977CD1E2A5170" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsGrantsinPeriodButNotReleasedWeightedAverageGrantDateFairValue" xlink:label="loc_ktos_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsGrantsinPeriodButNotReleasedWeightedAverageGrantDateFairValue_9DF0B2ABF6D7F4AF30BA77CD1E2B8081" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01B8F48F25173589AE5277CD1E2A07C7" xlink:to="loc_ktos_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsGrantsinPeriodButNotReleasedWeightedAverageGrantDateFairValue_9DF0B2ABF6D7F4AF30BA77CD1E2B8081" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/StockholdersEquityStockOptionPlansAndRestrictedStockUnitsPlansDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39ECBC08F5CA09376297F0E04C933BDE" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01A156775D290B0E58ABF0E04C9019CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39ECBC08F5CA09376297F0E04C933BDE" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01A156775D290B0E58ABF0E04C9019CA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_1AA62D562344D9358D99F0E04C91A5C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01A156775D290B0E58ABF0E04C9019CA" xlink:to="loc_us-gaap_PlanNameAxis_1AA62D562344D9358D99F0E04C91A5C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_44DFBF335755EBAA0DF1F0E04C91DBD8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_1AA62D562344D9358D99F0E04C91A5C8" xlink:to="loc_us-gaap_PlanNameDomain_44DFBF335755EBAA0DF1F0E04C91DBD8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_44DFBF335755EBAA0DF1F0E04C91DBD8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_1AA62D562344D9358D99F0E04C91A5C8" xlink:to="loc_us-gaap_PlanNameDomain_44DFBF335755EBAA0DF1F0E04C91DBD8" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_TwoThousandFourteenPlanMember" xlink:label="loc_ktos_TwoThousandFourteenPlanMember_7D3D1F8071B5B01CE8F6F0E04C91793A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_44DFBF335755EBAA0DF1F0E04C91DBD8" xlink:to="loc_ktos_TwoThousandFourteenPlanMember_7D3D1F8071B5B01CE8F6F0E04C91793A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_12FA5D48522914CC41FBF0E04C92614D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01A156775D290B0E58ABF0E04C9019CA" xlink:to="loc_us-gaap_AwardTypeAxis_12FA5D48522914CC41FBF0E04C92614D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B7F61BD3C17EB56153A0F0E04C9218BB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_12FA5D48522914CC41FBF0E04C92614D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B7F61BD3C17EB56153A0F0E04C9218BB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B7F61BD3C17EB56153A0F0E04C9218BB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_12FA5D48522914CC41FBF0E04C92614D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B7F61BD3C17EB56153A0F0E04C9218BB" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_StockOptionsAndRestrictedStockUnitsMember" xlink:label="loc_ktos_StockOptionsAndRestrictedStockUnitsMember_24DC2887F64B2FFB7602F0E04C92231A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B7F61BD3C17EB56153A0F0E04C9218BB" xlink:to="loc_ktos_StockOptionsAndRestrictedStockUnitsMember_24DC2887F64B2FFB7602F0E04C92231A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_06389C0C0195A26087E1F0E04C925CDA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_StockOptionsAndRestrictedStockUnitsMember_24DC2887F64B2FFB7602F0E04C92231A" xlink:to="loc_us-gaap_EmployeeStockOptionMember_06389C0C0195A26087E1F0E04C925CDA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_59651B3FE81F7267AB52F0E04C93DB31" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ktos_StockOptionsAndRestrictedStockUnitsMember_24DC2887F64B2FFB7602F0E04C92231A" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_59651B3FE81F7267AB52F0E04C93DB31" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_D9A0EB8A458554B0EF78F0E04C93DEDA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01A156775D290B0E58ABF0E04C9019CA" xlink:to="loc_srt_RangeAxis_D9A0EB8A458554B0EF78F0E04C93DEDA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_D8186657ED414B5492C6F0E04C937AA0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_D9A0EB8A458554B0EF78F0E04C93DEDA" xlink:to="loc_srt_RangeMember_D8186657ED414B5492C6F0E04C937AA0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_D8186657ED414B5492C6F0E04C937AA0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_D9A0EB8A458554B0EF78F0E04C93DEDA" xlink:to="loc_srt_RangeMember_D8186657ED414B5492C6F0E04C937AA0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_6F7F8477CC48D2F05F38F0E04C93EE3E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_D8186657ED414B5492C6F0E04C937AA0" xlink:to="loc_srt_MaximumMember_6F7F8477CC48D2F05F38F0E04C93EE3E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_0EF9D907A479261D0C70F0E04C9445FF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39ECBC08F5CA09376297F0E04C933BDE" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_0EF9D907A479261D0C70F0E04C9445FF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_3577F8CF1166B8AF59FAF0E04C943A21" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39ECBC08F5CA09376297F0E04C933BDE" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_3577F8CF1166B8AF59FAF0E04C943A21" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndOtherThanOptionsOutstandingNumber" xlink:label="loc_ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndOtherThanOptionsOutstandingNumber_4CBB2126DE39E8B7BA20F0E04C941C71" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39ECBC08F5CA09376297F0E04C933BDE" xlink:to="loc_ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndOtherThanOptionsOutstandingNumber_4CBB2126DE39E8B7BA20F0E04C941C71" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_09237EF8FADD8B3A466FF0E04C942771" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39ECBC08F5CA09376297F0E04C933BDE" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_09237EF8FADD8B3A466FF0E04C942771" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_1582DCC230A327A0DA5DF0E04C94FFA7" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39ECBC08F5CA09376297F0E04C933BDE" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_1582DCC230A327A0DA5DF0E04C94FFA7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_26DCACF28E814F03ECADF0E04C957DA3" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39ECBC08F5CA09376297F0E04C933BDE" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_26DCACF28E814F03ECADF0E04C957DA3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_DDE02AF17C249F213406F0E04C95074B" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39ECBC08F5CA09376297F0E04C933BDE" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_DDE02AF17C249F213406F0E04C95074B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_011F9B08FA27B0C2DE09F0E04C95849A" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39ECBC08F5CA09376297F0E04C933BDE" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_011F9B08FA27B0C2DE09F0E04C95849A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/StockholdersEquityStockOptionValuationAssumptionsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DA06392CA6AAB98E85EFEBB285E38F44" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_930D60028395E4AFA47EEBB285E2FB77" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DA06392CA6AAB98E85EFEBB285E38F44" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_930D60028395E4AFA47EEBB285E2FB77" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_EC82B41A78F595256746EBB285E278F4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_930D60028395E4AFA47EEBB285E2FB77" xlink:to="loc_us-gaap_AwardTypeAxis_EC82B41A78F595256746EBB285E278F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2E00695C04CD463D0766EBB285E2B8C4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_EC82B41A78F595256746EBB285E278F4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2E00695C04CD463D0766EBB285E2B8C4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2E00695C04CD463D0766EBB285E2B8C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_EC82B41A78F595256746EBB285E278F4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2E00695C04CD463D0766EBB285E2B8C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_A346E738A7D71436AE29EBB285E31B82" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2E00695C04CD463D0766EBB285E2B8C4" xlink:to="loc_us-gaap_EmployeeStockOptionMember_A346E738A7D71436AE29EBB285E31B82" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_1C0F401321AA10FB7D8EEBB285E3A128" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DA06392CA6AAB98E85EFEBB285E38F44" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_1C0F401321AA10FB7D8EEBB285E3A128" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_BE3CCE5841F2DFDD9AB4EBB285E3ECA4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DA06392CA6AAB98E85EFEBB285E38F44" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_BE3CCE5841F2DFDD9AB4EBB285E3ECA4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_CC796B0196B73F1B609DEBB285E35FBC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DA06392CA6AAB98E85EFEBB285E38F44" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_CC796B0196B73F1B609DEBB285E35FBC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_28BB53FF3C30EDB41593EBB285E47AFD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DA06392CA6AAB98E85EFEBB285E38F44" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_28BB53FF3C30EDB41593EBB285E47AFD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_25931AF85030EEFE0C11EBB285E423CD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DA06392CA6AAB98E85EFEBB285E38F44" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_25931AF85030EEFE0C11EBB285E423CD" xlink:type="arc" />
    <link:loc xlink:href="ktos-20191229.xsd#ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeitureRate" xlink:label="loc_ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeitureRate_BBA3196DD077E2559A51EBB285E4F888" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DA06392CA6AAB98E85EFEBB285E38F44" xlink:to="loc_ktos_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeitureRate_BBA3196DD077E2559A51EBB285E4F888" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_50BA395F3CEBD46EBED9EBB285E432E8" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DA06392CA6AAB98E85EFEBB285E38F44" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_50BA395F3CEBD46EBED9EBB285E432E8" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/StockholdersEquityStockOptionsRollForwardDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/StockholdersEquityStockholdersEquityTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SubsequentEvents" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:label="loc_us-gaap_SubsequentEventLineItems_82853E817773F5F3E6FE77CD1D7D959B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="loc_us-gaap_SubsequentEventTable_9F8816FDE3A21A3A228677CD1D7955B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_82853E817773F5F3E6FE77CD1D7D959B" xlink:to="loc_us-gaap_SubsequentEventTable_9F8816FDE3A21A3A228677CD1D7955B2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_AAFC73AD0DFCDC91EB1277CD1D7C6948" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_9F8816FDE3A21A3A228677CD1D7955B2" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_AAFC73AD0DFCDC91EB1277CD1D7C6948" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_923E204A2F591FDBD95477CD1D7CDF2B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_AAFC73AD0DFCDC91EB1277CD1D7C6948" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_923E204A2F591FDBD95477CD1D7CDF2B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_923E204A2F591FDBD95477CD1D7CDF2B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_AAFC73AD0DFCDC91EB1277CD1D7C6948" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_923E204A2F591FDBD95477CD1D7CDF2B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_01DED7437B8933E95C1D77CD1D7C091E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_923E204A2F591FDBD95477CD1D7CDF2B" xlink:to="loc_us-gaap_SubsequentEventMember_01DED7437B8933E95C1D77CD1D7C091E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_DBFFF2486E2DCB6FDF2077CD1D7DA765" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_82853E817773F5F3E6FE77CD1D7D959B" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_DBFFF2486E2DCB6FDF2077CD1D7DA765" xlink:type="arc" />
  </link:definitionLink>
</link:linkbase>
