<?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-20190929.xsd#Acquisition" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/AcquisitionAssetsAcquiredAndLiabilitiesAssumedDetails" xlink:href="ktos-20190929.xsd#AcquisitionAssetsAcquiredAndLiabilitiesAssumedDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/AcquisitionConsiderationPaidDetails" xlink:href="ktos-20190929.xsd#AcquisitionConsiderationPaidDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/AcquisitionNarrativeDetails" xlink:href="ktos-20190929.xsd#AcquisitionNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/AcquisitionProFormaFinancialInformationDetails" xlink:href="ktos-20190929.xsd#AcquisitionProFormaFinancialInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/AcquisitionTables" xlink:href="ktos-20190929.xsd#AcquisitionTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/CommitmentsAndContingencies" xlink:href="ktos-20190929.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/CondensedConsolidatedBalanceSheets" xlink:href="ktos-20190929.xsd#CondensedConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/CondensedConsolidatedBalanceSheetsParenthetical" xlink:href="ktos-20190929.xsd#CondensedConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/CondensedConsolidatedStatementsOfCashFlows" xlink:href="ktos-20190929.xsd#CondensedConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/CondensedConsolidatedStatementsOfOperationsAndComprehensiveIncomeLoss" xlink:href="ktos-20190929.xsd#CondensedConsolidatedStatementsOfOperationsAndComprehensiveIncomeLoss" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/CondensedConsolidatedStatementsOfStockholdersEquity" xlink:href="ktos-20190929.xsd#CondensedConsolidatedStatementsOfStockholdersEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/CoverPage" xlink:href="ktos-20190929.xsd#CoverPage" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/Debt" xlink:href="ktos-20190929.xsd#Debt" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DebtCreditAndSecurityAgreementDetails" xlink:href="ktos-20190929.xsd#DebtCreditAndSecurityAgreementDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DebtFairValueOfLongTermDebtDetails" xlink:href="ktos-20190929.xsd#DebtFairValueOfLongTermDebtDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DebtIssuanceOf65SeniorSecuredNotesDue2025Details" xlink:href="ktos-20190929.xsd#DebtIssuanceOf65SeniorSecuredNotesDue2025Details" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DebtTables" xlink:href="ktos-20190929.xsd#DebtTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DiscontinuedOperations" xlink:href="ktos-20190929.xsd#DiscontinuedOperations" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DiscontinuedOperationsAdditionalInformationDetails" xlink:href="ktos-20190929.xsd#DiscontinuedOperationsAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DiscontinuedOperationsAssetsAndLiabilitiesDetails" xlink:href="ktos-20190929.xsd#DiscontinuedOperationsAssetsAndLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DiscontinuedOperationsResultsOfDiscontinuedOperationsDetails" xlink:href="ktos-20190929.xsd#DiscontinuedOperationsResultsOfDiscontinuedOperationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/DiscontinuedOperationsTables" xlink:href="ktos-20190929.xsd#DiscontinuedOperationsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/GoodwillAndIntangibleAssets" xlink:href="ktos-20190929.xsd#GoodwillAndIntangibleAssets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/GoodwillAndIntangibleAssetsGoodwillDetails" xlink:href="ktos-20190929.xsd#GoodwillAndIntangibleAssetsGoodwillDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/GoodwillAndIntangibleAssetsPurchasedIntangibleAssetsDetails" xlink:href="ktos-20190929.xsd#GoodwillAndIntangibleAssetsPurchasedIntangibleAssetsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/GoodwillAndIntangibleAssetsTables" xlink:href="ktos-20190929.xsd#GoodwillAndIntangibleAssetsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxes" xlink:href="ktos-20190929.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxesAdditionalInformationDetails" xlink:href="ktos-20190929.xsd#IncomeTaxesAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxesIncomeTaxProvisionReconciliationDetails" xlink:href="ktos-20190929.xsd#IncomeTaxesIncomeTaxProvisionReconciliationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/IncomeTaxesTables" xlink:href="ktos-20190929.xsd#IncomeTaxesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/InventoriedCosts" xlink:href="ktos-20190929.xsd#InventoriedCosts" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/InventoriedCostsDetails" xlink:href="ktos-20190929.xsd#InventoriedCostsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/InventoriedCostsTables" xlink:href="ktos-20190929.xsd#InventoriedCostsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/Leases" xlink:href="ktos-20190929.xsd#Leases" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesAdditionalInformationDetails" xlink:href="ktos-20190929.xsd#LeasesAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesCashPaidDetails" xlink:href="ktos-20190929.xsd#LeasesCashPaidDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesLeaseExpenseDetails" xlink:href="ktos-20190929.xsd#LeasesLeaseExpenseDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesMaturitiesOfOperatingAndFinancingLeaseLiabilitiesDetails" xlink:href="ktos-20190929.xsd#LeasesMaturitiesOfOperatingAndFinancingLeaseLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesOperatingLeaseUnderAsc840Details" xlink:href="ktos-20190929.xsd#LeasesOperatingLeaseUnderAsc840Details" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesSupplementalBalanceSheetDetails" xlink:href="ktos-20190929.xsd#LeasesSupplementalBalanceSheetDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesTables" xlink:href="ktos-20190929.xsd#LeasesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/LeasesWeightedAverageDetails" xlink:href="ktos-20190929.xsd#LeasesWeightedAverageDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/NetIncomeLossPerCommonShare" xlink:href="ktos-20190929.xsd#NetIncomeLossPerCommonShare" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/NetIncomeLossPerCommonShareDetails" xlink:href="ktos-20190929.xsd#NetIncomeLossPerCommonShareDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RedeemableNoncontrollingInterest" xlink:href="ktos-20190929.xsd#RedeemableNoncontrollingInterest" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RedeemableNoncontrollingInterestDetails" xlink:href="ktos-20190929.xsd#RedeemableNoncontrollingInterestDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RevenueRecognition" xlink:href="ktos-20190929.xsd#RevenueRecognition" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails" xlink:href="ktos-20190929.xsd#RevenueRecognitionContractAssetsAndLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RevenueRecognitionDisaggregationOfRevenueDetails" xlink:href="ktos-20190929.xsd#RevenueRecognitionDisaggregationOfRevenueDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RevenueRecognitionNarrativeDetails" xlink:href="ktos-20190929.xsd#RevenueRecognitionNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RevenueRecognitionRemainingPerformanceObligationsDetails" xlink:href="ktos-20190929.xsd#RevenueRecognitionRemainingPerformanceObligationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/RevenueRecognitionTables" xlink:href="ktos-20190929.xsd#RevenueRecognitionTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SegmentInformation" xlink:href="ktos-20190929.xsd#SegmentInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SegmentInformationAdditionalInformationDetails" xlink:href="ktos-20190929.xsd#SegmentInformationAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SegmentInformationScheduleOfSegmentRevenuesDepreciationAndAmortizationAndOperatingLossDetails" xlink:href="ktos-20190929.xsd#SegmentInformationScheduleOfSegmentRevenuesDepreciationAndAmortizationAndOperatingLossDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SegmentInformationTables" xlink:href="ktos-20190929.xsd#SegmentInformationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SignificantCustomers" xlink:href="ktos-20190929.xsd#SignificantCustomers" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SignificantCustomersDetails" xlink:href="ktos-20190929.xsd#SignificantCustomersDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SummaryOfSignificantAccountingPolicies" xlink:href="ktos-20190929.xsd#SummaryOfSignificantAccountingPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SummaryOfSignificantAccountingPoliciesDetails" xlink:href="ktos-20190929.xsd#SummaryOfSignificantAccountingPoliciesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.kratosdefense.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:href="ktos-20190929.xsd#SummaryOfSignificantAccountingPoliciesPolicies" 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/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_27BEAA4F5B0D5EC095F55D667BF893FF" 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_638D6CFF12D45504B7BBC6D41415A104" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_638D6CFF12D45504B7BBC6D41415A104" 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_61E265208D675CC385CA7777C9ABCCAA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_638D6CFF12D45504B7BBC6D41415A104" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_61E265208D675CC385CA7777C9ABCCAA" 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_77C95B703F2F059B3E1BD8C067773A8C_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_61E265208D675CC385CA7777C9ABCCAA" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_77C95B703F2F059B3E1BD8C067773A8C_DA98DE3F87425575B530E4251D66B5F2" 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_37F88EEC24E654609DE1850D511F779D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_61E265208D675CC385CA7777C9ABCCAA" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_37F88EEC24E654609DE1850D511F779D" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_FTTIncMember" xlink:label="loc_ktos_FTTIncMember_45A8D37D0AB05CBA9F4A8FD0A78992E5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_37F88EEC24E654609DE1850D511F779D" xlink:to="loc_ktos_FTTIncMember_45A8D37D0AB05CBA9F4A8FD0A78992E5" 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_FC4A9BF3984B52CDA15ABA4A3E1B3391" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_FC4A9BF3984B52CDA15ABA4A3E1B3391" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsUnbilledReceivables" xlink:label="loc_ktos_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsUnbilledReceivables_59171C31C5AC57EFA022D4BA5F0BC5E9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_ktos_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsUnbilledReceivables_59171C31C5AC57EFA022D4BA5F0BC5E9" 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_884080A245765A978F57054E27C0830A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_884080A245765A978F57054E27C0830A" 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_F3C2AFF46EEE528B8276573C32C12AA2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_F3C2AFF46EEE528B8276573C32C12AA2" 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_80F9BE67E64D5022A0DA676F1B5EF799" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_80F9BE67E64D5022A0DA676F1B5EF799" 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_F42DB337A73E59BDAE7420F61CF667A3" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_F42DB337A73E59BDAE7420F61CF667A3" 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_F00FC22DE1E05C0590646CE413F06118" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_Goodwill_F00FC22DE1E05C0590646CE413F06118" 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_0C8C9D433FB858AC8BBA4AA0A3BC1FEE" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_0C8C9D433FB858AC8BBA4AA0A3BC1FEE" 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_C492E1FAFF6D5D49B4F1529E6153FE0B" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_C492E1FAFF6D5D49B4F1529E6153FE0B" 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_A743B874FBD15550BDDF82537697BE25" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_A743B874FBD15550BDDF82537697BE25" 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_C5DB1F831A7B539F919D80C354BA0655" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue_C5DB1F831A7B539F919D80C354BA0655" 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_8ACF70F791B653FB9E0AA9BCC9653E08" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_27BEAA4F5B0D5EC095F55D667BF893FF" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest_8ACF70F791B653FB9E0AA9BCC9653E08" 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_09CED004C4E05FD6ABB7D491753CD2E6" 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_D00EE62A62BF54429408323C91CACC2A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_09CED004C4E05FD6ABB7D491753CD2E6" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_D00EE62A62BF54429408323C91CACC2A" 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_897FA89880FA5C1C81060CAC68C64DB2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_D00EE62A62BF54429408323C91CACC2A" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_897FA89880FA5C1C81060CAC68C64DB2" 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_948D54DD9EA5D5D8B938D8C06790D4C7_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_897FA89880FA5C1C81060CAC68C64DB2" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_948D54DD9EA5D5D8B938D8C06790D4C7_DA98DE3F87425575B530E4251D66B5F2" 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_141EA2C6855F56048934EB903FDA79F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_897FA89880FA5C1C81060CAC68C64DB2" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_141EA2C6855F56048934EB903FDA79F2" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_FTTIncMember" xlink:label="loc_ktos_FTTIncMember_A08A14D6871953CBA7B466DD45E0A9B5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_141EA2C6855F56048934EB903FDA79F2" xlink:to="loc_ktos_FTTIncMember_A08A14D6871953CBA7B466DD45E0A9B5" 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_B521F278F9675F79923B47BB30401929" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_09CED004C4E05FD6ABB7D491753CD2E6" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_B521F278F9675F79923B47BB30401929" 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_2EAE3250501954E988D6E080775F7428" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_09CED004C4E05FD6ABB7D491753CD2E6" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_2EAE3250501954E988D6E080775F7428" 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_54AE74D7ED2C5BA78F75400C3F991CE4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_09CED004C4E05FD6ABB7D491753CD2E6" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_54AE74D7ED2C5BA78F75400C3F991CE4" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_BusinessCombinationConsiderationTransferredGross" xlink:label="loc_ktos_BusinessCombinationConsiderationTransferredGross_FD5F710070B85023A53BE09725367E2F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_09CED004C4E05FD6ABB7D491753CD2E6" xlink:to="loc_ktos_BusinessCombinationConsiderationTransferredGross_FD5F710070B85023A53BE09725367E2F" 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_57F8559FF6E95F758F3F83DDBBC58C51" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_09CED004C4E05FD6ABB7D491753CD2E6" xlink:to="loc_us-gaap_CashAcquiredFromAcquisition_57F8559FF6E95F758F3F83DDBBC58C51" 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_751CB51A9A2751F9A3B3CA23E9DDC993" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_09CED004C4E05FD6ABB7D491753CD2E6" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_751CB51A9A2751F9A3B3CA23E9DDC993" 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_924BEDD0217480FB03C31DD032D9EF1F" 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_792C5AA71B41D68244EA1DD032D5616E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_792C5AA71B41D68244EA1DD032D5616E" 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_6404D12A5569335C9DC31DD032D5C0FD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_792C5AA71B41D68244EA1DD032D5616E" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_6404D12A5569335C9DC31DD032D5C0FD" 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_1EF58A09E8A3CBC5EF781DD032D6AD06_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_6404D12A5569335C9DC31DD032D5C0FD" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1EF58A09E8A3CBC5EF781DD032D6AD06_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_1EF58A09E8A3CBC5EF781DD032D6AD06" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_6404D12A5569335C9DC31DD032D5C0FD" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1EF58A09E8A3CBC5EF781DD032D6AD06" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_FloridaTurbineTechnologiesInc.Member" xlink:label="loc_ktos_FloridaTurbineTechnologiesInc.Member_DA73B4246BAAC462426F1DD032D6349A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1EF58A09E8A3CBC5EF781DD032D6AD06" xlink:to="loc_ktos_FloridaTurbineTechnologiesInc.Member_DA73B4246BAAC462426F1DD032D6349A" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_FTTCoreLLCMember" xlink:label="loc_ktos_FTTCoreLLCMember_68F0EEB5E5AAC2E783361DD032D62E93" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1EF58A09E8A3CBC5EF781DD032D6AD06" xlink:to="loc_ktos_FTTCoreLLCMember_68F0EEB5E5AAC2E783361DD032D62E93" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_FTTIncMember" xlink:label="loc_ktos_FTTIncMember_EACEA078112F4F02597B1DD032D68162" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1EF58A09E8A3CBC5EF781DD032D6AD06" xlink:to="loc_ktos_FTTIncMember_EACEA078112F4F02597B1DD032D68162" 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_8D0A8376D84BE8DA7AC41DD032D69084" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_792C5AA71B41D68244EA1DD032D5616E" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_8D0A8376D84BE8DA7AC41DD032D69084" 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_E4DA4469CDA06802F05E1DD032D7B8B5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_8D0A8376D84BE8DA7AC41DD032D69084" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E4DA4469CDA06802F05E1DD032D7B8B5_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_E4DA4469CDA06802F05E1DD032D7B8B5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_8D0A8376D84BE8DA7AC41DD032D69084" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E4DA4469CDA06802F05E1DD032D7B8B5" 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_0F5013FBFF6EC25B348C1DD032D76028" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E4DA4469CDA06802F05E1DD032D7B8B5" xlink:to="loc_us-gaap_CustomerRelationshipsMember_0F5013FBFF6EC25B348C1DD032D76028" 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_30CE21830F4C60FA24651DD032D7D35F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E4DA4469CDA06802F05E1DD032D7B8B5" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_30CE21830F4C60FA24651DD032D7D35F" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_ContractsAndBacklogMember" xlink:label="loc_ktos_ContractsAndBacklogMember_62ABBB8659E5AA7D786E1DD032D76D40" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E4DA4469CDA06802F05E1DD032D7B8B5" xlink:to="loc_ktos_ContractsAndBacklogMember_62ABBB8659E5AA7D786E1DD032D76D40" 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_54F547434C34E434EC361DD032D7A6CD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E4DA4469CDA06802F05E1DD032D7B8B5" xlink:to="loc_us-gaap_TradeNamesMember_54F547434C34E434EC361DD032D7A6CD" 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_F8FC8AEE310D3F07DEBE1DD032D8AC18" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_792C5AA71B41D68244EA1DD032D5616E" xlink:to="loc_us-gaap_StatementClassOfStockAxis_F8FC8AEE310D3F07DEBE1DD032D8AC18" 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_2D487620FD849393241A1DD032D89A7B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_F8FC8AEE310D3F07DEBE1DD032D8AC18" xlink:to="loc_us-gaap_ClassOfStockDomain_2D487620FD849393241A1DD032D89A7B_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_2D487620FD849393241A1DD032D89A7B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_F8FC8AEE310D3F07DEBE1DD032D8AC18" xlink:to="loc_us-gaap_ClassOfStockDomain_2D487620FD849393241A1DD032D89A7B" 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_2C4A5E637D93CAAD80911DD032D8F51F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_2D487620FD849393241A1DD032D89A7B" xlink:to="loc_us-gaap_CommonStockMember_2C4A5E637D93CAAD80911DD032D8F51F" 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_D198CCE2A3BB2D6003C91DD032D9CB0E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_D198CCE2A3BB2D6003C91DD032D9CB0E" 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_419A8784B3E78F90FE041DD032D9A5E7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_419A8784B3E78F90FE041DD032D9A5E7" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_PaymentstoAcquireBusinessesGrossIncludingAmountsToBePaid" xlink:label="loc_ktos_PaymentstoAcquireBusinessesGrossIncludingAmountsToBePaid_D0BBB8822F859417AC181DD032D9F141" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_ktos_PaymentstoAcquireBusinessesGrossIncludingAmountsToBePaid_D0BBB8822F859417AC181DD032D9F141" 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_913DC83B9AFEB6DF98841DD032D9BEA0" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_913DC83B9AFEB6DF98841DD032D9BEA0" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_PaymentstoAcquireBusinessesAmountToBePaid" xlink:label="loc_ktos_PaymentstoAcquireBusinessesAmountToBePaid_DB8A9D6F93D960D011B91DD032D97B89" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_ktos_PaymentstoAcquireBusinessesAmountToBePaid_DB8A9D6F93D960D011B91DD032D97B89" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_PaymentstoAcquireBusinessesPaymentPeriod" xlink:label="loc_ktos_PaymentstoAcquireBusinessesPaymentPeriod_78B579C70BCA00BB64CD1DD032DA5B5C" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_ktos_PaymentstoAcquireBusinessesPaymentPeriod_78B579C70BCA00BB64CD1DD032DA5B5C" 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_A96FBBDED88D94D8FD681DD032DA5440" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_A96FBBDED88D94D8FD681DD032DA5440" 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_98C4D2039C8397CD31F21DD032DFCDF2" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned_98C4D2039C8397CD31F21DD032DFCDF2" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_IncreaseInMinorityInterestPurchasePriceOverNext12Months" xlink:label="loc_ktos_IncreaseInMinorityInterestPurchasePriceOverNext12Months_4B3F1C54F426E5F1B72E1DD032DFD9AD" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_ktos_IncreaseInMinorityInterestPurchasePriceOverNext12Months_4B3F1C54F426E5F1B72E1DD032DFD9AD" 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_F9F3C08E439E338D5E8F1DD032DFD054" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_F9F3C08E439E338D5E8F1DD032DFD054" 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_0D6428F88F1B5CEB88481DD032DFD381" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_0D6428F88F1B5CEB88481DD032DFD381" 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_19DCDDB2F74EC40DE1E11DD032E03FB1" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_19DCDDB2F74EC40DE1E11DD032E03FB1" 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_E6F50A3C0AD5FB48B7361DD032E05FFC" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_DeferredTaxLiabilities_E6F50A3C0AD5FB48B7361DD032E05FFC" 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_82EB3F86098CBB34F63A1DD032E0FC88" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_82EB3F86098CBB34F63A1DD032E0FC88" 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_17105C30BD808467FDCC1DD032E0A999" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_17105C30BD808467FDCC1DD032E0A999" 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_1F8D303FE6580ECA978F1DD032E059C1" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_924BEDD0217480FB03C31DD032D9EF1F" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_1F8D303FE6580ECA978F1DD032E059C1" 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_2677974361425D49B561EBC5DBF7FB9E" 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_8E426EB3F1215AC38C5EEA969FD313F0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2677974361425D49B561EBC5DBF7FB9E" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_8E426EB3F1215AC38C5EEA969FD313F0" 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_280C088A0A675969B3C4CDC704054418" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_8E426EB3F1215AC38C5EEA969FD313F0" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_280C088A0A675969B3C4CDC704054418" 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_3554493241AD33035903D8C0673D5595_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_280C088A0A675969B3C4CDC704054418" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3554493241AD33035903D8C0673D5595_DA98DE3F87425575B530E4251D66B5F2" 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_E0EFBB42CA4E5DF084676A464BDEAC80" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_280C088A0A675969B3C4CDC704054418" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_E0EFBB42CA4E5DF084676A464BDEAC80" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_FTTIncMember" xlink:label="loc_ktos_FTTIncMember_4C98F86F92DA5E00941B940546CB8E8A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_E0EFBB42CA4E5DF084676A464BDEAC80" xlink:to="loc_ktos_FTTIncMember_4C98F86F92DA5E00941B940546CB8E8A" 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_A04639F8AB255919A8182757A78FB21D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2677974361425D49B561EBC5DBF7FB9E" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_A04639F8AB255919A8182757A78FB21D" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_BusinessAcquisitionProFormaIncomeLossfromContinuingOperationsBeforeTax" xlink:label="loc_ktos_BusinessAcquisitionProFormaIncomeLossfromContinuingOperationsBeforeTax_8609B75AC548520ABA622055E744E13F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2677974361425D49B561EBC5DBF7FB9E" xlink:to="loc_ktos_BusinessAcquisitionProFormaIncomeLossfromContinuingOperationsBeforeTax_8609B75AC548520ABA622055E744E13F" 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_2077D32CAA4F52FCA382D899FB8A39E7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2677974361425D49B561EBC5DBF7FB9E" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_2077D32CAA4F52FCA382D899FB8A39E7" 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_E5992D26DD105CAABFBFC9F9952F017C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2677974361425D49B561EBC5DBF7FB9E" xlink:to="loc_us-gaap_NetIncomeLoss_E5992D26DD105CAABFBFC9F9952F017C" 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_FA5B63073306504AA04D528CEADAF74B" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2677974361425D49B561EBC5DBF7FB9E" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic_FA5B63073306504AA04D528CEADAF74B" 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_D791B8B5C9025420A9DF834982ADE8D7" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2677974361425D49B561EBC5DBF7FB9E" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted_D791B8B5C9025420A9DF834982ADE8D7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/AcquisitionTables" 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/CondensedConsolidatedBalanceSheets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/CondensedConsolidatedBalanceSheetsParenthetical" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/CondensedConsolidatedStatementsOfCashFlows" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/CondensedConsolidatedStatementsOfOperationsAndComprehensiveIncomeLoss" 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_98DDCC35E7F8BA0AD4761DD03354F839" 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_10E1949379870D3086E71DD0335315DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_StatementTable_10E1949379870D3086E71DD0335315DD" 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_1A9AABC2944E480BC8BC1DD0335355A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_10E1949379870D3086E71DD0335315DD" xlink:to="loc_srt_ProductOrServiceAxis_1A9AABC2944E480BC8BC1DD0335355A1" 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_AD2A88A485C37147E2001DD0335485C9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_1A9AABC2944E480BC8BC1DD0335355A1" xlink:to="loc_srt_ProductsAndServicesDomain_AD2A88A485C37147E2001DD0335485C9_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_AD2A88A485C37147E2001DD0335485C9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_1A9AABC2944E480BC8BC1DD0335355A1" xlink:to="loc_srt_ProductsAndServicesDomain_AD2A88A485C37147E2001DD0335485C9" 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_6B2BE8F590B1E4F69C2C1DD033547F3F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_AD2A88A485C37147E2001DD0335485C9" xlink:to="loc_us-gaap_ServiceMember_6B2BE8F590B1E4F69C2C1DD033547F3F" 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_FEECD14BFCCD304540861DD03354B539" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_AD2A88A485C37147E2001DD0335485C9" xlink:to="loc_us-gaap_ProductMember_FEECD14BFCCD304540861DD03354B539" 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_5DC6B27A0DEF92F591B11DD03355A8AF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_5DC6B27A0DEF92F591B11DD03355A8AF" 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_3D92F3392CC92329FD681DD033555ACD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_3D92F3392CC92329FD681DD033555ACD" 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_D850674BFB52AA8ECFEE1DD03355678D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_GrossProfit_D850674BFB52AA8ECFEE1DD03355678D" 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_052F66F49A05B61BACD91DD033555469" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_052F66F49A05B61BACD91DD033555469" 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_7F4ECF57DE95451660BD1DD033554BA8" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_7F4ECF57DE95451660BD1DD033554BA8" 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_0311CB4D5F48FBD7FA1A1DD03355E391" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_0311CB4D5F48FBD7FA1A1DD03355E391" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_ImpairmentChargesAndAdjustmentsToUnusedOfficeSpaceLiability" xlink:label="loc_ktos_ImpairmentChargesAndAdjustmentsToUnusedOfficeSpaceLiability_4484C9FC42CCB4D61D791DD03355FD48" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_ktos_ImpairmentChargesAndAdjustmentsToUnusedOfficeSpaceLiability_4484C9FC42CCB4D61D791DD03355FD48" 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_6743B967FE19C1128C031DD0335500D4" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_OperatingIncomeLoss_6743B967FE19C1128C031DD0335500D4" 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_7814107EE108A0438B001DD03355DA45" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7814107EE108A0438B001DD03355DA45" 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_55B75CB15690D5E58EDD1DD033550F5E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7814107EE108A0438B001DD03355DA45" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_55B75CB15690D5E58EDD1DD033550F5E" 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_4711C1C9319C9A5EC7461DD03355326A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7814107EE108A0438B001DD03355DA45" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_4711C1C9319C9A5EC7461DD03355326A" 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_A9ADBA65DFE35961C0021DD033562246" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7814107EE108A0438B001DD03355DA45" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_A9ADBA65DFE35961C0021DD033562246" 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_80FE49D338478E7DB0CF1DD033562001" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_80FE49D338478E7DB0CF1DD033562001" 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_AC333BA8DEB12E8FAA611DD03356BFBE" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_AC333BA8DEB12E8FAA611DD03356BFBE" 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_AC07038D865574906E751DD0335685CE" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_AC07038D865574906E751DD0335685CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAbstract" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAbstract_C5A25F42AD18AED0E64C1DD0335660B9" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAbstract_C5A25F42AD18AED0E64C1DD0335660B9" 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_2B14BE560100144747501DD03357BCDF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAbstract_C5A25F42AD18AED0E64C1DD0335660B9" xlink:to="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_2B14BE560100144747501DD03357BCDF" 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_31FC4D5C2C7A831725581DD033579263" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAbstract_C5A25F42AD18AED0E64C1DD0335660B9" xlink:to="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_31FC4D5C2C7A831725581DD033579263" 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_8F1FE1737BB6D5BD536E1DD03357A3C3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAbstract_C5A25F42AD18AED0E64C1DD0335660B9" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_8F1FE1737BB6D5BD536E1DD03357A3C3" 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_625804F9E19169834FA21DD033575658" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_ProfitLoss_625804F9E19169834FA21DD033575658" 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_AFA8045ED6DBA76FFB181DD033575C85" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_AFA8045ED6DBA76FFB181DD033575C85" 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_D20E31C4B761A374C86F1DD03357B113" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_NetIncomeLoss_D20E31C4B761A374C86F1DD03357B113" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_A59D8E5EFF8544A6F0E11DD03358A930" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_A59D8E5EFF8544A6F0E11DD03358A930" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsPerBasicAndDilutedShare" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicAndDilutedShare_D5042463498B029F5D951DD03358296F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_A59D8E5EFF8544A6F0E11DD03358A930" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicAndDilutedShare_D5042463498B029F5D951DD03358296F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicAndDilutedShare" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicAndDilutedShare_36B69D83C44A2751B5511DD033585B12" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_A59D8E5EFF8544A6F0E11DD03358A930" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicAndDilutedShare_36B69D83C44A2751B5511DD033585B12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDiluted_4A942B758350A6B06C7D1DD03358DCE7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_A59D8E5EFF8544A6F0E11DD03358A930" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDiluted_4A942B758350A6B06C7D1DD03358DCE7" 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_FBEF0672B64293ADAD7B1DD03358FF5E" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_EarningsPerShareDilutedAbstract_FBEF0672B64293ADAD7B1DD03358FF5E" 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_B2835E2FA6F903A8299A1DD0335849D8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_FBEF0672B64293ADAD7B1DD03358FF5E" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_B2835E2FA6F903A8299A1DD0335849D8" 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_C30701C8E4A0F880FBB91DD033592864" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_FBEF0672B64293ADAD7B1DD03358FF5E" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare_C30701C8E4A0F880FBB91DD033592864" 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_46FBFFDFA8CF37D1BA071DD033596505" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_FBEF0672B64293ADAD7B1DD03358FF5E" xlink:to="loc_us-gaap_EarningsPerShareDiluted_46FBFFDFA8CF37D1BA071DD033596505" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_3B56FA4EA43F03B551E51DD03359ECCC" xlink:type="locator" />
    <link:definitionArc order="19" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_3B56FA4EA43F03B551E51DD03359ECCC" 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_25EF064DCD2E546910811DD033591303" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_3B56FA4EA43F03B551E51DD03359ECCC" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_25EF064DCD2E546910811DD033591303" 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_CD3C26C14D1395568B811DD033595892" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_3B56FA4EA43F03B551E51DD03359ECCC" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_CD3C26C14D1395568B811DD033595892" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_F119F205B95C2FA9F76E1DD0335A37B1" xlink:type="locator" />
    <link:definitionArc order="20" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_98DDCC35E7F8BA0AD4761DD03354F839" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_F119F205B95C2FA9F76E1DD0335A37B1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_6579120B12EBDC9BB0921DD0335AAC26" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_F119F205B95C2FA9F76E1DD0335A37B1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_6579120B12EBDC9BB0921DD0335AAC26" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_E4A81041873D44C4C22D1DD0335A7272" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_F119F205B95C2FA9F76E1DD0335A37B1" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_E4A81041873D44C4C22D1DD0335A7272" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_CB52D2E41C9C17190B711DD0335AA99C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_F119F205B95C2FA9F76E1DD0335A37B1" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_CB52D2E41C9C17190B711DD0335AA99C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_242497091BCE4E6067EA1DD0335ABFF5" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_F119F205B95C2FA9F76E1DD0335A37B1" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_242497091BCE4E6067EA1DD0335ABFF5" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/CondensedConsolidatedStatementsOfStockholdersEquity" 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_88C85882B9EA79A63F07375057701A55" 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_BE505D027D039303399F3750576DB75A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_88C85882B9EA79A63F07375057701A55" xlink:to="loc_us-gaap_StatementTable_BE505D027D039303399F3750576DB75A" 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_5ACBDF46CC15E3F81DAB3750576DB697" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_BE505D027D039303399F3750576DB75A" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_5ACBDF46CC15E3F81DAB3750576DB697" 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_EB14F3195DDB4A1382A63750576D6F08_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_5ACBDF46CC15E3F81DAB3750576DB697" xlink:to="loc_us-gaap_EquityComponentDomain_EB14F3195DDB4A1382A63750576D6F08_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_EB14F3195DDB4A1382A63750576D6F08" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_5ACBDF46CC15E3F81DAB3750576DB697" xlink:to="loc_us-gaap_EquityComponentDomain_EB14F3195DDB4A1382A63750576D6F08" 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_AC805D817D20931D1FB63750576E6641" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EB14F3195DDB4A1382A63750576D6F08" xlink:to="loc_us-gaap_NoncontrollingInterestMember_AC805D817D20931D1FB63750576E6641" 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_369A70BF060E4CCCA2B43750576E7D1C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EB14F3195DDB4A1382A63750576D6F08" xlink:to="loc_us-gaap_CommonStockMember_369A70BF060E4CCCA2B43750576E7D1C" 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_01619D9D4F5E2F9243283750576FA7CF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EB14F3195DDB4A1382A63750576D6F08" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_01619D9D4F5E2F9243283750576FA7CF" 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_03611C713A57AA6460AC3750576F883D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EB14F3195DDB4A1382A63750576D6F08" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_03611C713A57AA6460AC3750576F883D" 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_2D020CCC8DD2B1A0191B3750576F7C12" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EB14F3195DDB4A1382A63750576D6F08" xlink:to="loc_us-gaap_RetainedEarningsMember_2D020CCC8DD2B1A0191B3750576F7C12" 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_6AE5F9532A19D3C3773D3750576F758B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_BE505D027D039303399F3750576DB75A" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_6AE5F9532A19D3C3773D3750576F758B" 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_ED846BEE45095910C73A3750576F38FA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_6AE5F9532A19D3C3773D3750576F758B" xlink:to="loc_us-gaap_TypeOfAdoptionMember_ED846BEE45095910C73A3750576F38FA_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_ED846BEE45095910C73A3750576F38FA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_6AE5F9532A19D3C3773D3750576F758B" xlink:to="loc_us-gaap_TypeOfAdoptionMember_ED846BEE45095910C73A3750576F38FA" 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_FC7B5C62EB903FD3A0B43750576FB0F0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_ED846BEE45095910C73A3750576F38FA" xlink:to="loc_us-gaap_AccountingStandardsUpdate201409Member_FC7B5C62EB903FD3A0B43750576FB0F0" 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_2C9DEF04DF1F00F9A05E3750577015FF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_88C85882B9EA79A63F07375057701A55" xlink:to="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_2C9DEF04DF1F00F9A05E3750577015FF" 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_943F19FA5E73A050C070375057707EC3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_2C9DEF04DF1F00F9A05E3750577015FF" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_943F19FA5E73A050C070375057707EC3" 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_48A96AAD2FF93916FAE037505771E530" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_88C85882B9EA79A63F07375057701A55" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" 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_A9A3861554B747144C3A37505771DA99" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_A9A3861554B747144C3A37505771DA99" 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_A9CCE0C0BAA20267C73B37505771C79F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_A9CCE0C0BAA20267C73B37505771C79F" 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_3FCB43185CF4AFC1DFC637505771C999" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption_3FCB43185CF4AFC1DFC637505771C999" 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_659E41DEB9BE1DBA841F37505772C2BA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_659E41DEB9BE1DBA841F37505772C2BA" 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_129FF5D350D2DFC4C340375057722ADB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_129FF5D350D2DFC4C340375057722ADB" 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_19F2100D4BE39968455F37505772B47B" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_19F2100D4BE39968455F37505772B47B" 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_4184567DA670F129B28F37505772983C" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings_4184567DA670F129B28F37505772983C" 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_DE670A276793563123613750577259A8" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings_DE670A276793563123613750577259A8" 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_FEFD50628BB34E43A6033750577238BD" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_FEFD50628BB34E43A6033750577238BD" 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_DDFA822FBED6899E4731375057734320" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_DDFA822FBED6899E4731375057734320" 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_7054F343DF371BEFE0E1375057737910" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_NetIncomeLoss_7054F343DF371BEFE0E1375057737910" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_67A4E89D0E7BA43242C337505773A81B" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_67A4E89D0E7BA43242C337505773A81B" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_OtherComprehensiveIncomeLossForeignCurrencyTransactionandTranslationAdjustmentNetofTax1" xlink:label="loc_ktos_OtherComprehensiveIncomeLossForeignCurrencyTransactionandTranslationAdjustmentNetofTax1_C72671B9375978D9D86437575346D6BC" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_ktos_OtherComprehensiveIncomeLossForeignCurrencyTransactionandTranslationAdjustmentNetofTax1_C72671B9375978D9D86437575346D6BC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncontrollingInterestIncreaseFromBusinessCombination" xlink:label="loc_us-gaap_NoncontrollingInterestIncreaseFromBusinessCombination_EB430B0CB900D08DA93037505773DF7C" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_48A96AAD2FF93916FAE037505771E530" xlink:to="loc_us-gaap_NoncontrollingInterestIncreaseFromBusinessCombination_EB430B0CB900D08DA93037505773DF7C" 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_A2D5CFE69A835276B3B4BFDDF35C21D0" 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_08BB044014DD59FABE6268F5B6CDABC6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A2D5CFE69A835276B3B4BFDDF35C21D0" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_08BB044014DD59FABE6268F5B6CDABC6" 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_2080B842BC9C57D3B1DD4AB9E4C51025" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_08BB044014DD59FABE6268F5B6CDABC6" xlink:to="loc_us-gaap_CreditFacilityAxis_2080B842BC9C57D3B1DD4AB9E4C51025" 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_9C1F903839FC2A37F585D8C0662EFCA0_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_2080B842BC9C57D3B1DD4AB9E4C51025" xlink:to="loc_us-gaap_CreditFacilityDomain_9C1F903839FC2A37F585D8C0662EFCA0_DA98DE3F87425575B530E4251D66B5F2" 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_B05724C181745C4E8251F815DB1C05BE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_2080B842BC9C57D3B1DD4AB9E4C51025" xlink:to="loc_us-gaap_CreditFacilityDomain_B05724C181745C4E8251F815DB1C05BE" 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_B6C4FAB02D1A5819B5D107B344A06B89" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_B05724C181745C4E8251F815DB1C05BE" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_B6C4FAB02D1A5819B5D107B344A06B89" 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_FAC569C5DBA753E5988F4C8BA770A40C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_B05724C181745C4E8251F815DB1C05BE" xlink:to="loc_us-gaap_LetterOfCreditMember_FAC569C5DBA753E5988F4C8BA770A40C" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_SwingLineLoanMember" xlink:label="loc_ktos_SwingLineLoanMember_78AA8E7284E45D309826F18419E1B0F5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_B05724C181745C4E8251F815DB1C05BE" xlink:to="loc_ktos_SwingLineLoanMember_78AA8E7284E45D309826F18419E1B0F5" 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_2B08E6BB56725B3489C407A400E38154" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_08BB044014DD59FABE6268F5B6CDABC6" xlink:to="loc_us-gaap_VariableRateAxis_2B08E6BB56725B3489C407A400E38154" 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_5BFBE50F40F4E7369F62D8C0662FAB9B_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_2B08E6BB56725B3489C407A400E38154" xlink:to="loc_us-gaap_VariableRateDomain_5BFBE50F40F4E7369F62D8C0662FAB9B_DA98DE3F87425575B530E4251D66B5F2" 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_BC7DE36A5BDD5C18A1CEE255A1509350" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_2B08E6BB56725B3489C407A400E38154" xlink:to="loc_us-gaap_VariableRateDomain_BC7DE36A5BDD5C18A1CEE255A1509350" 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_557EDA685F9C5C31B99DA50096F6A71F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_BC7DE36A5BDD5C18A1CEE255A1509350" xlink:to="loc_us-gaap_FederalFundsEffectiveSwapRateMember_557EDA685F9C5C31B99DA50096F6A71F" 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_8A42528E67875AD2A63D08F307045B94" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_BC7DE36A5BDD5C18A1CEE255A1509350" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_8A42528E67875AD2A63D08F307045B94" 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_08254169D96659998F98F9FA48FC5349" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_BC7DE36A5BDD5C18A1CEE255A1509350" xlink:to="loc_us-gaap_BaseRateMember_08254169D96659998F98F9FA48FC5349" 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_A87B9CB10F235F7F837BAD386C51D02A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_BC7DE36A5BDD5C18A1CEE255A1509350" xlink:to="loc_us-gaap_EurodollarMember_A87B9CB10F235F7F837BAD386C51D02A" 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_7EF3C36A7671535DBCD0D8D7A961CF9B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_08BB044014DD59FABE6268F5B6CDABC6" xlink:to="loc_srt_RangeAxis_7EF3C36A7671535DBCD0D8D7A961CF9B" 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_1258FC7F7EF5F6DD2885D8C0663021F0_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_7EF3C36A7671535DBCD0D8D7A961CF9B" xlink:to="loc_srt_RangeMember_1258FC7F7EF5F6DD2885D8C0663021F0_DA98DE3F87425575B530E4251D66B5F2" 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_0306FBC869C85654B2EAB6DB7FDFB4B0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_7EF3C36A7671535DBCD0D8D7A961CF9B" xlink:to="loc_srt_RangeMember_0306FBC869C85654B2EAB6DB7FDFB4B0" 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_CD194DB72BC658CE9F9D5D64A8893C51" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_0306FBC869C85654B2EAB6DB7FDFB4B0" xlink:to="loc_srt_MinimumMember_CD194DB72BC658CE9F9D5D64A8893C51" 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_708C4B28CC8B5BC092497F89456FFF7A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_0306FBC869C85654B2EAB6DB7FDFB4B0" xlink:to="loc_srt_MaximumMember_708C4B28CC8B5BC092497F89456FFF7A" 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_2817E0A11B1E5EFDB896534084A63322" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A2D5CFE69A835276B3B4BFDDF35C21D0" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_2817E0A11B1E5EFDB896534084A63322" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_DebtInstrumentMaturityPeriod" xlink:label="loc_ktos_DebtInstrumentMaturityPeriod_961874A8B6ED5BFCB26ABBBEDF26CC0C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A2D5CFE69A835276B3B4BFDDF35C21D0" xlink:to="loc_ktos_DebtInstrumentMaturityPeriod_961874A8B6ED5BFCB26ABBBEDF26CC0C" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_LineOfCreditFacilityMaximumPossibleBorrowingsSubjectToApplicationAndBankApproval" xlink:label="loc_ktos_LineOfCreditFacilityMaximumPossibleBorrowingsSubjectToApplicationAndBankApproval_76DEA721F28C5DE084B459B295FE09DB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A2D5CFE69A835276B3B4BFDDF35C21D0" xlink:to="loc_ktos_LineOfCreditFacilityMaximumPossibleBorrowingsSubjectToApplicationAndBankApproval_76DEA721F28C5DE084B459B295FE09DB" 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_AB5B86533AA75E5CAE2DFB1ECA48E54D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A2D5CFE69A835276B3B4BFDDF35C21D0" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_AB5B86533AA75E5CAE2DFB1ECA48E54D" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_DebtInstrumentFixedChargeCoverageRatio" xlink:label="loc_ktos_DebtInstrumentFixedChargeCoverageRatio_C72C56BA5F2F5D5DA27C2DCB210BCC3C" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A2D5CFE69A835276B3B4BFDDF35C21D0" xlink:to="loc_ktos_DebtInstrumentFixedChargeCoverageRatio_C72C56BA5F2F5D5DA27C2DCB210BCC3C" 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_CBFFFEEB32D25C71A17F3A817D1B6059" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A2D5CFE69A835276B3B4BFDDF35C21D0" xlink:to="loc_us-gaap_LineOfCredit_CBFFFEEB32D25C71A17F3A817D1B6059" 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_8CAC7ACD3E0D5AEDA99BCA3E3EFA4587" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_A2D5CFE69A835276B3B4BFDDF35C21D0" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_8CAC7ACD3E0D5AEDA99BCA3E3EFA4587" 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_668738265EF75C9197C3B58A940D42F2" 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_C2F3EC18EF705453BC1A9B50BD2D949E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_668738265EF75C9197C3B58A940D42F2" xlink:to="loc_us-gaap_DebtInstrumentTable_C2F3EC18EF705453BC1A9B50BD2D949E" 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_70164B757D4F5D6DA9D2114DFC48764E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_C2F3EC18EF705453BC1A9B50BD2D949E" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_70164B757D4F5D6DA9D2114DFC48764E" 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_A513DA37B84C47BE70BBD8C06693F7EE_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_70164B757D4F5D6DA9D2114DFC48764E" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_A513DA37B84C47BE70BBD8C06693F7EE_DA98DE3F87425575B530E4251D66B5F2" 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_4489A43980AC537CA822FA7CCABD42D9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_70164B757D4F5D6DA9D2114DFC48764E" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4489A43980AC537CA822FA7CCABD42D9" 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_09F68231FF6B576EBC499F2C12433EF6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4489A43980AC537CA822FA7CCABD42D9" xlink:to="loc_us-gaap_SeniorNotesMember_09F68231FF6B576EBC499F2C12433EF6" 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_DBD67C5180735D58A3EE5A4283876C61" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_C2F3EC18EF705453BC1A9B50BD2D949E" xlink:to="loc_us-gaap_DebtInstrumentAxis_DBD67C5180735D58A3EE5A4283876C61" 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_B0CE62281CD31FAC14C5D8C066941E32_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_DBD67C5180735D58A3EE5A4283876C61" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_B0CE62281CD31FAC14C5D8C066941E32_DA98DE3F87425575B530E4251D66B5F2" 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_3E9647811EAC5286B4328089D6F70010" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_DBD67C5180735D58A3EE5A4283876C61" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3E9647811EAC5286B4328089D6F70010" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_SixPointFivePercentSeniorSecuredNotesDue2025Member" xlink:label="loc_ktos_SixPointFivePercentSeniorSecuredNotesDue2025Member_044BF2EA944A56C29E434D07155459ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3E9647811EAC5286B4328089D6F70010" xlink:to="loc_ktos_SixPointFivePercentSeniorSecuredNotesDue2025Member_044BF2EA944A56C29E434D07155459ED" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_SevenPercentSeniorNotesDue2019Member" xlink:label="loc_ktos_SevenPercentSeniorNotesDue2019Member_3BB0A0AAD83F590AB9D4E03363BE93F6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3E9647811EAC5286B4328089D6F70010" xlink:to="loc_ktos_SevenPercentSeniorNotesDue2019Member_3BB0A0AAD83F590AB9D4E03363BE93F6" 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_0DDBE820CD0D5657B479DC517ED12A38" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_C2F3EC18EF705453BC1A9B50BD2D949E" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_0DDBE820CD0D5657B479DC517ED12A38" 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_83FE54C3F59F9A4A7E72D8C06695F1EF_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_0DDBE820CD0D5657B479DC517ED12A38" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_83FE54C3F59F9A4A7E72D8C06695F1EF_DA98DE3F87425575B530E4251D66B5F2" 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_5DBAE6A9F31757B09156B690D55933B4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_0DDBE820CD0D5657B479DC517ED12A38" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_5DBAE6A9F31757B09156B690D55933B4" 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_2F62E423FF715218BB65978A55418124" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_5DBAE6A9F31757B09156B690D55933B4" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_2F62E423FF715218BB65978A55418124" 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_16EAF635BC385ED9A268D1C4EC905822" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_5DBAE6A9F31757B09156B690D55933B4" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_16EAF635BC385ED9A268D1C4EC905822" 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_A1DAA8627CB55535A078D53410503B13" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_668738265EF75C9197C3B58A940D42F2" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_A1DAA8627CB55535A078D53410503B13" 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_E1B2943660D55377A2FAE25ED1025279" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_668738265EF75C9197C3B58A940D42F2" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_E1B2943660D55377A2FAE25ED1025279" 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_7C7C68B13C0C5315B5C6877C48753A05" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_668738265EF75C9197C3B58A940D42F2" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_7C7C68B13C0C5315B5C6877C48753A05" 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_A9A292ED4325599BA32BF4D7B5561985" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_668738265EF75C9197C3B58A940D42F2" xlink:to="loc_us-gaap_DebtInstrumentRepurchaseAmount_A9A292ED4325599BA32BF4D7B5561985" 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_DA654AEA94C351EBB8D162F4CBDFE25A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_668738265EF75C9197C3B58A940D42F2" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedPremium_DA654AEA94C351EBB8D162F4CBDFE25A" 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_2B2FEC20267254DE844B09A06D95057A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_668738265EF75C9197C3B58A940D42F2" xlink:to="loc_us-gaap_DebtInstrumentIncreaseAccruedInterest_2B2FEC20267254DE844B09A06D95057A" 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_94C95B4DC8B35E7B970A2EE8926DAF50" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_668738265EF75C9197C3B58A940D42F2" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_94C95B4DC8B35E7B970A2EE8926DAF50" 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_8B7762763C545A1B951271E671B11AD1" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_668738265EF75C9197C3B58A940D42F2" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_8B7762763C545A1B951271E671B11AD1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebt" xlink:label="loc_us-gaap_LongTermDebt_DA767503A4FF5FA89BF390D2AFE9BF62" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_668738265EF75C9197C3B58A940D42F2" xlink:to="loc_us-gaap_LongTermDebt_DA767503A4FF5FA89BF390D2AFE9BF62" 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/DiscontinuedOperationsAdditionalInformationDetails" 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_7D533A1B372A560F444B1FE369B70EAA" 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_391B4832753B21954D361FE369B4632A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_7D533A1B372A560F444B1FE369B70EAA" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_391B4832753B21954D361FE369B4632A" 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_0D6B8807BF220BC2A2DA1FE369B538EC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_391B4832753B21954D361FE369B4632A" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_0D6B8807BF220BC2A2DA1FE369B538EC" 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_43A44E0962BCFB405D961FE369B5A1F6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_0D6B8807BF220BC2A2DA1FE369B538EC" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_43A44E0962BCFB405D961FE369B5A1F6_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_43A44E0962BCFB405D961FE369B5A1F6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_0D6B8807BF220BC2A2DA1FE369B538EC" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_43A44E0962BCFB405D961FE369B5A1F6" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_PublicSafetyAndSecurityMember" xlink:label="loc_ktos_PublicSafetyAndSecurityMember_4D7E43EEEE56DE08FD7D1FE369B524AD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_43A44E0962BCFB405D961FE369B5A1F6" xlink:to="loc_ktos_PublicSafetyAndSecurityMember_4D7E43EEEE56DE08FD7D1FE369B524AD" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_HerleyIndustriesIncMember" xlink:label="loc_ktos_HerleyIndustriesIncMember_A540D3F8D84F39B8F7201FE369B50200" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_43A44E0962BCFB405D961FE369B5A1F6" xlink:to="loc_ktos_HerleyIndustriesIncMember_A540D3F8D84F39B8F7201FE369B50200" 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_1BB5F8516661F61C347C1FE369B65544" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_391B4832753B21954D361FE369B4632A" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_1BB5F8516661F61C347C1FE369B65544" 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_E55D33109F83BF8F99461FE369B6C872_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_1BB5F8516661F61C347C1FE369B65544" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_E55D33109F83BF8F99461FE369B6C872_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_E55D33109F83BF8F99461FE369B6C872" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_1BB5F8516661F61C347C1FE369B65544" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_E55D33109F83BF8F99461FE369B6C872" 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_72E924A6A3C340732B141FE369B6B4CF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_E55D33109F83BF8F99461FE369B6C872" xlink:to="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_72E924A6A3C340732B141FE369B6B4CF" 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_C0233134A41E2F760E041FE369B6E72F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_E55D33109F83BF8F99461FE369B6C872" xlink:to="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_C0233134A41E2F760E041FE369B6E72F" 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_EA7A5B65C18735237F031FE369B784A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_7D533A1B372A560F444B1FE369B70EAA" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_EA7A5B65C18735237F031FE369B784A1" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationWorkingCapitalAdjustment" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationWorkingCapitalAdjustment_A8F4D6DEA267673C98C71FE369B729A8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_7D533A1B372A560F444B1FE369B70EAA" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationWorkingCapitalAdjustment_A8F4D6DEA267673C98C71FE369B729A8" 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_10E4B450789ED348BE741FE369B709AC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_7D533A1B372A560F444B1FE369B70EAA" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_10E4B450789ED348BE741FE369B709AC" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_DivestitureofBusinessesWorkingCapitalRetained" xlink:label="loc_ktos_DivestitureofBusinessesWorkingCapitalRetained_6B2C61B0C625912669061FE369B74C62" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_7D533A1B372A560F444B1FE369B70EAA" xlink:to="loc_ktos_DivestitureofBusinessesWorkingCapitalRetained_6B2C61B0C625912669061FE369B74C62" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationTransactionCosts" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationTransactionCosts_735EDBF6D84E2A8BAB351FE369B7BE28" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_7D533A1B372A560F444B1FE369B70EAA" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationTransactionCosts_735EDBF6D84E2A8BAB351FE369B7BE28" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationImpactOnRevenueOfProjectCostAdjustments" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationImpactOnRevenueOfProjectCostAdjustments_F2821A71560BB246CE8C1FE369B8F211" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_7D533A1B372A560F444B1FE369B70EAA" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationImpactOnRevenueOfProjectCostAdjustments_F2821A71560BB246CE8C1FE369B8F211" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationImpactOnOperatingIncomeLossOfProjectCostAdjustments" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationImpactOnOperatingIncomeLossOfProjectCostAdjustments_9945C7660B217331BEB11FE369B888AB" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_7D533A1B372A560F444B1FE369B70EAA" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationImpactOnOperatingIncomeLossOfProjectCostAdjustments_9945C7660B217331BEB11FE369B888AB" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationTransactionRelatedCost" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationTransactionRelatedCost_4DB6FA4F2866EA8726051FE369B8EE4F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_7D533A1B372A560F444B1FE369B70EAA" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationTransactionRelatedCost_4DB6FA4F2866EA8726051FE369B8EE4F" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationGainFromTaxLiability" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationGainFromTaxLiability_74FAB4B48564F143B53F1FE369B83D9B" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_7D533A1B372A560F444B1FE369B70EAA" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationGainFromTaxLiability_74FAB4B48564F143B53F1FE369B83D9B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/DiscontinuedOperationsAssetsAndLiabilitiesDetails" 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_AF483B90BC69536D9DE1B91457D9D495" 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_A32C655163F2586FA1516E71ED6C941E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_AF483B90BC69536D9DE1B91457D9D495" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A32C655163F2586FA1516E71ED6C941E" 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_9B28FF1EA3855459A19FCCB0FB4875EC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A32C655163F2586FA1516E71ED6C941E" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_9B28FF1EA3855459A19FCCB0FB4875EC" 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_DCF34C705BBFFE19559CD8C0675678DB_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_9B28FF1EA3855459A19FCCB0FB4875EC" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_DCF34C705BBFFE19559CD8C0675678DB_DA98DE3F87425575B530E4251D66B5F2" 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_7E0937E89BF65F36B9C2C9C852F4404B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_9B28FF1EA3855459A19FCCB0FB4875EC" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_7E0937E89BF65F36B9C2C9C852F4404B" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_HerleyIndustriesIncMember" xlink:label="loc_ktos_HerleyIndustriesIncMember_C3B252EB226D526F84C0A3B75E63B1E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_7E0937E89BF65F36B9C2C9C852F4404B" xlink:to="loc_ktos_HerleyIndustriesIncMember_C3B252EB226D526F84C0A3B75E63B1E0" 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_A9A0BF316C225BAA824FB0B2955E9F19" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_A32C655163F2586FA1516E71ED6C941E" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_A9A0BF316C225BAA824FB0B2955E9F19" 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_3E8B073B811D7A2C12B2D8C06757F1FB_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_A9A0BF316C225BAA824FB0B2955E9F19" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_3E8B073B811D7A2C12B2D8C06757F1FB_DA98DE3F87425575B530E4251D66B5F2" 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_D180E28B2B195AEF92CEBA99700CDC30" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_A9A0BF316C225BAA824FB0B2955E9F19" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_D180E28B2B195AEF92CEBA99700CDC30" 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_5BD2555C597556A3B4EFB5A7999DC37B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_D180E28B2B195AEF92CEBA99700CDC30" xlink:to="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_5BD2555C597556A3B4EFB5A7999DC37B" 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_F43B9858850952DFB308DC407A696171" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_AF483B90BC69536D9DE1B91457D9D495" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet_F43B9858850952DFB308DC407A696171" 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_4599270AC24558EBA6990AF8D8295F74" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_AF483B90BC69536D9DE1B91457D9D495" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets_4599270AC24558EBA6990AF8D8295F74" 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_578134BE77615ADBAFC9CA25F122A588" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_AF483B90BC69536D9DE1B91457D9D495" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent_578134BE77615ADBAFC9CA25F122A588" 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_907FC2036AA65DAE90C67B949355B5D9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_AF483B90BC69536D9DE1B91457D9D495" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayableCurrent_907FC2036AA65DAE90C67B949355B5D9" 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_F8BAF93A5A9B5AF6AA075204A1A9C0A7" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_AF483B90BC69536D9DE1B91457D9D495" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilitiesCurrent_F8BAF93A5A9B5AF6AA075204A1A9C0A7" 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_26BCBF24C5015EE7A6D5BA0B7927897C" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_AF483B90BC69536D9DE1B91457D9D495" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities_26BCBF24C5015EE7A6D5BA0B7927897C" 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_2A62012EF4C15BFCB2218E655E84BE55" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_AF483B90BC69536D9DE1B91457D9D495" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent_2A62012EF4C15BFCB2218E655E84BE55" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationNoncurrent" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationNoncurrent_EE280777074F5A4CA5A519BA12F3BEDF" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_AF483B90BC69536D9DE1B91457D9D495" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationNoncurrent_EE280777074F5A4CA5A519BA12F3BEDF" 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_48D65A6BD2C37CD3A6EDFE5A0A8CDB24" 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_E2C0890CF4F447DA5B86FE5A0A8B7A64" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_48D65A6BD2C37CD3A6EDFE5A0A8CDB24" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_E2C0890CF4F447DA5B86FE5A0A8B7A64" 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_CF12BFA3EC6E02042BCBFE5A0A8B3C84" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_E2C0890CF4F447DA5B86FE5A0A8B7A64" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_CF12BFA3EC6E02042BCBFE5A0A8B3C84" 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_615DC91D17850FB2976AFE5A0A8B9A2F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_CF12BFA3EC6E02042BCBFE5A0A8B3C84" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_615DC91D17850FB2976AFE5A0A8B9A2F_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_615DC91D17850FB2976AFE5A0A8B9A2F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_CF12BFA3EC6E02042BCBFE5A0A8B3C84" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_615DC91D17850FB2976AFE5A0A8B9A2F" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_HerleyIndustriesIncMember" xlink:label="loc_ktos_HerleyIndustriesIncMember_69A9F31E591CB49452CCFE5A0A8B946B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_615DC91D17850FB2976AFE5A0A8B9A2F" xlink:to="loc_ktos_HerleyIndustriesIncMember_69A9F31E591CB49452CCFE5A0A8B946B" 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_12D367E0E6686DE09E11FE5A0A8C59A2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_E2C0890CF4F447DA5B86FE5A0A8B7A64" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_12D367E0E6686DE09E11FE5A0A8C59A2" 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_1F1863A4A986B77DDFCBFE5A0A8C717C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_12D367E0E6686DE09E11FE5A0A8C59A2" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_1F1863A4A986B77DDFCBFE5A0A8C717C_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_1F1863A4A986B77DDFCBFE5A0A8C717C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_12D367E0E6686DE09E11FE5A0A8C59A2" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_1F1863A4A986B77DDFCBFE5A0A8C717C" 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_7F1A4EEA8752A1D055B8FE5A0A8CF1EA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_1F1863A4A986B77DDFCBFE5A0A8C717C" xlink:to="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_7F1A4EEA8752A1D055B8FE5A0A8CF1EA" 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_8FEBAF5BC75A5F21A19BFE5A0A8C3C9F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_48D65A6BD2C37CD3A6EDFE5A0A8CDB24" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_8FEBAF5BC75A5F21A19BFE5A0A8C3C9F" 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_F8F9983C0CB4C96B3C98FE5A0A8D67A7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_48D65A6BD2C37CD3A6EDFE5A0A8CDB24" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold_F8F9983C0CB4C96B3C98FE5A0A8D67A7" 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_9F87D7BE03D64FB94B56FE5A0A8D8C5F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_48D65A6BD2C37CD3A6EDFE5A0A8CDB24" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense_9F87D7BE03D64FB94B56FE5A0A8D8C5F" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense" xlink:label="loc_ktos_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense_39A99F26EC904C7F00D0FE5A0A8D8DD8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_48D65A6BD2C37CD3A6EDFE5A0A8CDB24" xlink:to="loc_ktos_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense_39A99F26EC904C7F00D0FE5A0A8D8DD8" 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_85E273E97F997916C77DFE5A0A8DC840" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_48D65A6BD2C37CD3A6EDFE5A0A8CDB24" xlink:to="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodBeforeIncomeTax_85E273E97F997916C77DFE5A0A8DC840" 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_83F92E80AFBD81274D0CFE5A0A8D4520" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_48D65A6BD2C37CD3A6EDFE5A0A8CDB24" xlink:to="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_83F92E80AFBD81274D0CFE5A0A8D4520" 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_7B9638C741F576347EC4FE5A0A8E9652" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_48D65A6BD2C37CD3A6EDFE5A0A8CDB24" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_7B9638C741F576347EC4FE5A0A8E9652" 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/GoodwillAndIntangibleAssets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/GoodwillAndIntangibleAssetsGoodwillDetails" 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_997A65CD243F5F209A99918AB8A94261" 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_0E93B27E91F8573CB71968F0E023F17B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_997A65CD243F5F209A99918AB8A94261" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_0E93B27E91F8573CB71968F0E023F17B" 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_8F7A90D9412852209B76C866DD97BA28" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_0E93B27E91F8573CB71968F0E023F17B" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_8F7A90D9412852209B76C866DD97BA28" 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_5F9D95B97CD2D9FB03C7D8C066E5D84F_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_8F7A90D9412852209B76C866DD97BA28" xlink:to="loc_us-gaap_SegmentDomain_5F9D95B97CD2D9FB03C7D8C066E5D84F_DA98DE3F87425575B530E4251D66B5F2" 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_AF451EF3917F53CC964AD8E682785100" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_8F7A90D9412852209B76C866DD97BA28" xlink:to="loc_us-gaap_SegmentDomain_AF451EF3917F53CC964AD8E682785100" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_KratosGovernmentSolutionsMember" xlink:label="loc_ktos_KratosGovernmentSolutionsMember_D2A18344D143593EAF7040D2AC5B11E4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_AF451EF3917F53CC964AD8E682785100" xlink:to="loc_ktos_KratosGovernmentSolutionsMember_D2A18344D143593EAF7040D2AC5B11E4" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_KratosUnmannedSystemsMember" xlink:label="loc_ktos_KratosUnmannedSystemsMember_561ECF46B09156649CB1AD33EE91A6CB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_AF451EF3917F53CC964AD8E682785100" xlink:to="loc_ktos_KratosUnmannedSystemsMember_561ECF46B09156649CB1AD33EE91A6CB" 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_70712BDEDE005065AE5F194AF4D0BF7B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_997A65CD243F5F209A99918AB8A94261" xlink:to="loc_us-gaap_GoodwillGross_70712BDEDE005065AE5F194AF4D0BF7B" 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_2D850179456450EA96873157B854432C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_997A65CD243F5F209A99918AB8A94261" xlink:to="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLoss_2D850179456450EA96873157B854432C" 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_61A7D8A115955FEBA817E4DC23A0F968" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_997A65CD243F5F209A99918AB8A94261" xlink:to="loc_us-gaap_Goodwill_61A7D8A115955FEBA817E4DC23A0F968" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/GoodwillAndIntangibleAssetsPurchasedIntangibleAssetsDetails" 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_F55249A823DE2125A312A5370857D7C9" 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_C30BF9E5E35813C83D8FA5370857DB38" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_F55249A823DE2125A312A5370857D7C9" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_C30BF9E5E35813C83D8FA5370857DB38" 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_27C509539E4294D1B36BA53708575796" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_C30BF9E5E35813C83D8FA5370857DB38" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_27C509539E4294D1B36BA53708575796" 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_EB77C125B002FF1A0700A5370857A977_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_27C509539E4294D1B36BA53708575796" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EB77C125B002FF1A0700A5370857A977_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_EB77C125B002FF1A0700A5370857A977" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_27C509539E4294D1B36BA53708575796" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EB77C125B002FF1A0700A5370857A977" 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_2A8FD1C84EEA16C0F807A537085703CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EB77C125B002FF1A0700A5370857A977" xlink:to="loc_us-gaap_CustomerRelationshipsMember_2A8FD1C84EEA16C0F807A537085703CA" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_ContractsAndBacklogMember" xlink:label="loc_ktos_ContractsAndBacklogMember_C9B75D2DA595D2909EDEA5370857C8A0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EB77C125B002FF1A0700A5370857A977" xlink:to="loc_ktos_ContractsAndBacklogMember_C9B75D2DA595D2909EDEA5370857C8A0" 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_D94D7B4E299736DCC8AAA5370857CE0A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EB77C125B002FF1A0700A5370857A977" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_D94D7B4E299736DCC8AAA5370857CE0A" 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_F02DF0A7666BA1C29E09A53708579B52" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EB77C125B002FF1A0700A5370857A977" xlink:to="loc_us-gaap_TradeNamesMember_F02DF0A7666BA1C29E09A53708579B52" 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_7B181813C4BAF5BF464AA53708575BF2" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_EB77C125B002FF1A0700A5370857A977" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_7B181813C4BAF5BF464AA53708575BF2" 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_F900F63668BF428A0A6BA5370857AEB2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_C30BF9E5E35813C83D8FA5370857DB38" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_F900F63668BF428A0A6BA5370857AEB2" 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_6A6118B3D6905EF2F99EA5E477572F31_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_F900F63668BF428A0A6BA5370857AEB2" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6A6118B3D6905EF2F99EA5E477572F31_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_6A6118B3D6905EF2F99EA5E477572F31" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_F900F63668BF428A0A6BA5370857AEB2" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6A6118B3D6905EF2F99EA5E477572F31" 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_8BF40F74B1AA491DEE3BA5E240B4D2CC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6A6118B3D6905EF2F99EA5E477572F31" xlink:to="loc_us-gaap_TradeNamesMember_8BF40F74B1AA491DEE3BA5E240B4D2CC" 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_5D8031CF1CCF0E6DAEEBA5370857226C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_F55249A823DE2125A312A5370857D7C9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_5D8031CF1CCF0E6DAEEBA5370857226C" 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_2DC794CBF96EB105B9EEA53708575A7A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_5D8031CF1CCF0E6DAEEBA5370857226C" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_2DC794CBF96EB105B9EEA53708575A7A" 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_A84858EFFDC41B6C63F1A5370857B533" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_5D8031CF1CCF0E6DAEEBA5370857226C" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_A84858EFFDC41B6C63F1A5370857B533" 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_99E0458A30D12B30A215A5370857B435" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_5D8031CF1CCF0E6DAEEBA5370857226C" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_99E0458A30D12B30A215A5370857B435" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_IntangibleAssetsExcludingGoodwillGross" xlink:label="loc_ktos_IntangibleAssetsExcludingGoodwillGross_8289573DA1026DDE47FBA5370857BD52" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_F55249A823DE2125A312A5370857D7C9" xlink:to="loc_ktos_IntangibleAssetsExcludingGoodwillGross_8289573DA1026DDE47FBA5370857BD52" 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_EE0379D7F9290CF8764BA53708570629" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_F55249A823DE2125A312A5370857D7C9" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_EE0379D7F9290CF8764BA53708570629" 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_15978DBB2DB3909B997CA5370857B301" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_F55249A823DE2125A312A5370857D7C9" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_15978DBB2DB3909B997CA5370857B301" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/GoodwillAndIntangibleAssetsTables" 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/IncomeTaxesAdditionalInformationDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/IncomeTaxesIncomeTaxProvisionReconciliationDetails" 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/InventoriedCosts" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/InventoriedCostsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/InventoriedCostsTables" 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_6159B06DC4CC544BBC48B5DBA61ABBB1" 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_8241B46F74ED5B13A15F5CD404F09067" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_6159B06DC4CC544BBC48B5DBA61ABBB1" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_8241B46F74ED5B13A15F5CD404F09067" 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_A19BED3DA3CB58E097C3314B03AC4FF3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_8241B46F74ED5B13A15F5CD404F09067" xlink:to="loc_srt_StatementGeographicalAxis_A19BED3DA3CB58E097C3314B03AC4FF3" 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_EAA0B76840C31DAB8B813E8337C4F30C_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_A19BED3DA3CB58E097C3314B03AC4FF3" xlink:to="loc_srt_SegmentGeographicalDomain_EAA0B76840C31DAB8B813E8337C4F30C_DA98DE3F87425575B530E4251D66B5F2" 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_03DEDD8913E15C9E9570B372BB0D5AFD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_A19BED3DA3CB58E097C3314B03AC4FF3" xlink:to="loc_srt_SegmentGeographicalDomain_03DEDD8913E15C9E9570B372BB0D5AFD" 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_4B06A020130A5D06AD2E24F28BB33500" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_03DEDD8913E15C9E9570B372BB0D5AFD" xlink:to="loc_stpr_CO_4B06A020130A5D06AD2E24F28BB33500" 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_1B75070177F254C5BDDD6CCA95B28E33" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_6159B06DC4CC544BBC48B5DBA61ABBB1" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAsset_1B75070177F254C5BDDD6CCA95B28E33" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeasesRentExpenseNet" xlink:label="loc_us-gaap_OperatingLeasesRentExpenseNet_493229E2B9AB5BE8AA448FFE37F09589" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_6159B06DC4CC544BBC48B5DBA61ABBB1" xlink:to="loc_us-gaap_OperatingLeasesRentExpenseNet_493229E2B9AB5BE8AA448FFE37F09589" 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_9C1AA4CCAFB75F55A2BD1ACF23244955" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_6159B06DC4CC544BBC48B5DBA61ABBB1" xlink:to="loc_us-gaap_OperatingLeasesIncomeStatementSubleaseRevenue_9C1AA4CCAFB75F55A2BD1ACF23244955" 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/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/LeasesTables" 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/NetIncomeLossPerCommonShareDetails" 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_2935852D094856389E73CDA50B53F014" 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_70FCF6CC0A1B5B3E80CF799DD022089D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_2935852D094856389E73CDA50B53F014" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_70FCF6CC0A1B5B3E80CF799DD022089D" 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_4E1A172772725F5FA46C26346B873699" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_70FCF6CC0A1B5B3E80CF799DD022089D" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_4E1A172772725F5FA46C26346B873699" 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_B7B2A5C42EC0372E793FD8C065E6C277_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_4E1A172772725F5FA46C26346B873699" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_B7B2A5C42EC0372E793FD8C065E6C277_DA98DE3F87425575B530E4251D66B5F2" 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_6DE7C74751E154F5BEE4DDCC90ABBEB7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_4E1A172772725F5FA46C26346B873699" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_6DE7C74751E154F5BEE4DDCC90ABBEB7" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_StockOptionsAndStockAwardsMember" xlink:label="loc_ktos_StockOptionsAndStockAwardsMember_604609EFDD0A51069044D80006AB2F0C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_6DE7C74751E154F5BEE4DDCC90ABBEB7" xlink:to="loc_ktos_StockOptionsAndStockAwardsMember_604609EFDD0A51069044D80006AB2F0C" 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_D01A9D55539B5D8E81313BEFA23717A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_2935852D094856389E73CDA50B53F014" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_D01A9D55539B5D8E81313BEFA23717A2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RedeemableNoncontrollingInterest" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RedeemableNoncontrollingInterestDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MinorityInterestLineItems" xlink:label="loc_us-gaap_MinorityInterestLineItems_DFEC7A849C3059529D43D31BF610FEF6" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MinorityInterestTable" xlink:label="loc_us-gaap_MinorityInterestTable_EF4F8D32B1445FA083C0FD6FC7D42342" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_DFEC7A849C3059529D43D31BF610FEF6" xlink:to="loc_us-gaap_MinorityInterestTable_EF4F8D32B1445FA083C0FD6FC7D42342" 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_066CD39EAA26547AB4A60B8E2897FFED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_EF4F8D32B1445FA083C0FD6FC7D42342" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_066CD39EAA26547AB4A60B8E2897FFED" 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_FF64B3F47E0386DAC1521AD0C59EB483_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_066CD39EAA26547AB4A60B8E2897FFED" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_FF64B3F47E0386DAC1521AD0C59EB483_DA98DE3F87425575B530E4251D66B5F2" 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_3AEC9570B1A953EB88A80F489C38B746" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_066CD39EAA26547AB4A60B8E2897FFED" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3AEC9570B1A953EB88A80F489C38B746" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_FTTIncMember" xlink:label="loc_ktos_FTTIncMember_5EDE3F30D3D956EC8F5FF737FB78982E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3AEC9570B1A953EB88A80F489C38B746" xlink:to="loc_ktos_FTTIncMember_5EDE3F30D3D956EC8F5FF737FB78982E" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_IncreaseInMinorityInterestPurchasePriceOverNext12Months" xlink:label="loc_ktos_IncreaseInMinorityInterestPurchasePriceOverNext12Months_DFE25C43210D51BEA365EA272E13FD0F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_DFEC7A849C3059529D43D31BF610FEF6" xlink:to="loc_ktos_IncreaseInMinorityInterestPurchasePriceOverNext12Months_DFE25C43210D51BEA365EA272E13FD0F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RevenueRecognition" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RevenueRecognitionDisaggregationOfRevenueDetails" 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_8CF0C82598765F99A33CC4995D4502B8" 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_D1DA08B70E9E53CA96D390F4CA965515" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_8CF0C82598765F99A33CC4995D4502B8" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_D1DA08B70E9E53CA96D390F4CA965515" 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_A90526AD6430586481D1D2328B3C5D52" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_D1DA08B70E9E53CA96D390F4CA965515" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_A90526AD6430586481D1D2328B3C5D52" 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_537783E29FC13355A5F0D8C0660A68B1_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_A90526AD6430586481D1D2328B3C5D52" xlink:to="loc_us-gaap_SegmentDomain_537783E29FC13355A5F0D8C0660A68B1_DA98DE3F87425575B530E4251D66B5F2" 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_8A1A8EAD5E435E549D9F58BEBC581DE5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_A90526AD6430586481D1D2328B3C5D52" xlink:to="loc_us-gaap_SegmentDomain_8A1A8EAD5E435E549D9F58BEBC581DE5" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_KratosGovernmentSolutionsMember" xlink:label="loc_ktos_KratosGovernmentSolutionsMember_7A263FCABA405B6B80040F09E30C0D0C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_8A1A8EAD5E435E549D9F58BEBC581DE5" xlink:to="loc_ktos_KratosGovernmentSolutionsMember_7A263FCABA405B6B80040F09E30C0D0C" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_KratosUnmannedSystemsMember" xlink:label="loc_ktos_KratosUnmannedSystemsMember_5EF537D1BF985A18A10EF1203A196743" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_8A1A8EAD5E435E549D9F58BEBC581DE5" xlink:to="loc_ktos_KratosUnmannedSystemsMember_5EF537D1BF985A18A10EF1203A196743" 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_B17E4285DF1D565EB4424D1C532790CA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_D1DA08B70E9E53CA96D390F4CA965515" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_B17E4285DF1D565EB4424D1C532790CA" 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_27BE7C9191B2303CACC1D8C0660C86F5_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_B17E4285DF1D565EB4424D1C532790CA" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_27BE7C9191B2303CACC1D8C0660C86F5_DA98DE3F87425575B530E4251D66B5F2" 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_CA6169A0B2C057C3A791FE26D9EAACD3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_B17E4285DF1D565EB4424D1C532790CA" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_CA6169A0B2C057C3A791FE26D9EAACD3" 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_C6D95410C3CB527CB3881D50B5A10546" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_CA6169A0B2C057C3A791FE26D9EAACD3" xlink:to="loc_us-gaap_FixedPriceContractMember_C6D95410C3CB527CB3881D50B5A10546" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_CostPlusFeeContractMember" xlink:label="loc_ktos_CostPlusFeeContractMember_26D6480BBD03563595F04228CF5B677F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_CA6169A0B2C057C3A791FE26D9EAACD3" xlink:to="loc_ktos_CostPlusFeeContractMember_26D6480BBD03563595F04228CF5B677F" 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_E46C0477903E5D06BEE9DA38461E88B7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_CA6169A0B2C057C3A791FE26D9EAACD3" xlink:to="loc_us-gaap_TimeAndMaterialsContractMember_E46C0477903E5D06BEE9DA38461E88B7" 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_81AFAA25E3155AF7B156A45BD7D79B31" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_D1DA08B70E9E53CA96D390F4CA965515" xlink:to="loc_srt_MajorCustomersAxis_81AFAA25E3155AF7B156A45BD7D79B31" 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_43B79D79B99DC170F6A4D8C0660D0389_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_81AFAA25E3155AF7B156A45BD7D79B31" xlink:to="loc_srt_NameOfMajorCustomerDomain_43B79D79B99DC170F6A4D8C0660D0389_DA98DE3F87425575B530E4251D66B5F2" 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_381F86BB6D5159698F64D64E680A66C0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_81AFAA25E3155AF7B156A45BD7D79B31" xlink:to="loc_srt_NameOfMajorCustomerDomain_381F86BB6D5159698F64D64E680A66C0" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_UnitedStatesGovernmentMember" xlink:label="loc_ktos_UnitedStatesGovernmentMember_2711F82662035E7C8EFCE62F4A2F2742" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_381F86BB6D5159698F64D64E680A66C0" xlink:to="loc_ktos_UnitedStatesGovernmentMember_2711F82662035E7C8EFCE62F4A2F2742" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_NonUSGovernmentMember" xlink:label="loc_ktos_NonUSGovernmentMember_F5D8877D22AD5948A3D2C7495AEED5D3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_381F86BB6D5159698F64D64E680A66C0" xlink:to="loc_ktos_NonUSGovernmentMember_F5D8877D22AD5948A3D2C7495AEED5D3" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_USCommercialMember" xlink:label="loc_ktos_USCommercialMember_7F25656BFF625B9193B92147CED6D2D7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_381F86BB6D5159698F64D64E680A66C0" xlink:to="loc_ktos_USCommercialMember_7F25656BFF625B9193B92147CED6D2D7" 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_78521BD6038B570E89A900FF286314A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_8CF0C82598765F99A33CC4995D4502B8" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_78521BD6038B570E89A900FF286314A3" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RevenueRecognitionNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RevenueRecognitionRemainingPerformanceObligationsDetails" 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_34839EFE84805815B1CCC2BF614F837B" 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_63DB1DB636DB5A94A70C6F5DD5D6FE95" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_34839EFE84805815B1CCC2BF614F837B" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_63DB1DB636DB5A94A70C6F5DD5D6FE95" 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_907C15FC044750E3B37A94BDCC2F015E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_63DB1DB636DB5A94A70C6F5DD5D6FE95" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_907C15FC044750E3B37A94BDCC2F015E" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercentage" xlink:label="loc_ktos_RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercentage_61ADBC964B6E5E1782F25AB2A9CE2179" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_34839EFE84805815B1CCC2BF614F837B" xlink:to="loc_ktos_RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercentage_61ADBC964B6E5E1782F25AB2A9CE2179" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/RevenueRecognitionTables" 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/SegmentInformationAdditionalInformationDetails" 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_95F0C4BF57FC5C13880C3B16E3C50E19" 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_3781F4A859625F5DBCBE71B9CDA0EBC9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_95F0C4BF57FC5C13880C3B16E3C50E19" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_3781F4A859625F5DBCBE71B9CDA0EBC9" 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_41C3271D23FA5B798B676F18F95E3AB2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_3781F4A859625F5DBCBE71B9CDA0EBC9" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_41C3271D23FA5B798B676F18F95E3AB2" 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_6FF70087CF2C08000EBB1AD0C5B3A29B_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_41C3271D23FA5B798B676F18F95E3AB2" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6FF70087CF2C08000EBB1AD0C5B3A29B_DA98DE3F87425575B530E4251D66B5F2" 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_3215B30843FF59D9A32B3581568151BE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_41C3271D23FA5B798B676F18F95E3AB2" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3215B30843FF59D9A32B3581568151BE" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_FTTIncMember" xlink:label="loc_ktos_FTTIncMember_A544136409D95C8094BDC5204E129D4A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3215B30843FF59D9A32B3581568151BE" xlink:to="loc_ktos_FTTIncMember_A544136409D95C8094BDC5204E129D4A" 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_BEB5CC3C8F0D5B4589D5D5AC678C128B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_95F0C4BF57FC5C13880C3B16E3C50E19" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_BEB5CC3C8F0D5B4589D5D5AC678C128B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SegmentInformationScheduleOfSegmentRevenuesDepreciationAndAmortizationAndOperatingLossDetails" 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_5C129FC726F36A99CA061DD031AFE6CF" 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_46348A6D297D03FBB17C1DD031AAB4A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_5C129FC726F36A99CA061DD031AFE6CF" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_46348A6D297D03FBB17C1DD031AAB4A0" 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_B2CACC9672264CEF3AB81DD031AA739F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_46348A6D297D03FBB17C1DD031AAB4A0" xlink:to="loc_srt_ProductOrServiceAxis_B2CACC9672264CEF3AB81DD031AA739F" 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_79A458EBC76A24F19DE71DD031AADCB0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_B2CACC9672264CEF3AB81DD031AA739F" xlink:to="loc_srt_ProductsAndServicesDomain_79A458EBC76A24F19DE71DD031AADCB0_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_79A458EBC76A24F19DE71DD031AADCB0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_B2CACC9672264CEF3AB81DD031AA739F" xlink:to="loc_srt_ProductsAndServicesDomain_79A458EBC76A24F19DE71DD031AADCB0" 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_65339A5A916C2E937BFC1DD031AB6141" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_79A458EBC76A24F19DE71DD031AADCB0" xlink:to="loc_us-gaap_ServiceMember_65339A5A916C2E937BFC1DD031AB6141" 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_9CF45F4F8E516A5B85541DD031AB3C24" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_79A458EBC76A24F19DE71DD031AADCB0" xlink:to="loc_us-gaap_ProductMember_9CF45F4F8E516A5B85541DD031AB3C24" 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_775B4205A888E62A7CC01DD031AB3618" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_46348A6D297D03FBB17C1DD031AAB4A0" xlink:to="loc_srt_ConsolidationItemsAxis_775B4205A888E62A7CC01DD031AB3618" 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_54E2277B82B1AC60301B1DD031ABC796_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_775B4205A888E62A7CC01DD031AB3618" xlink:to="loc_srt_ConsolidationItemsDomain_54E2277B82B1AC60301B1DD031ABC796_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_54E2277B82B1AC60301B1DD031ABC796" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_775B4205A888E62A7CC01DD031AB3618" xlink:to="loc_srt_ConsolidationItemsDomain_54E2277B82B1AC60301B1DD031ABC796" 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_3F555D3BFFD2159FC5721DD031AB9FE7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_54E2277B82B1AC60301B1DD031ABC796" xlink:to="loc_us-gaap_OperatingSegmentsMember_3F555D3BFFD2159FC5721DD031AB9FE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateNonSegmentMember" xlink:label="loc_us-gaap_CorporateNonSegmentMember_48E7B6EB9A7B343C67311DD031AC28F6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_54E2277B82B1AC60301B1DD031ABC796" xlink:to="loc_us-gaap_CorporateNonSegmentMember_48E7B6EB9A7B343C67311DD031AC28F6" 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_AED31290408F2089A3641DD031AEB1F9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_46348A6D297D03FBB17C1DD031AAB4A0" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_AED31290408F2089A3641DD031AEB1F9" 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_73B63C6848E4F1FA36AF1DD031AEAEA1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_AED31290408F2089A3641DD031AEB1F9" xlink:to="loc_us-gaap_SegmentDomain_73B63C6848E4F1FA36AF1DD031AEAEA1_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_73B63C6848E4F1FA36AF1DD031AEAEA1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_AED31290408F2089A3641DD031AEB1F9" xlink:to="loc_us-gaap_SegmentDomain_73B63C6848E4F1FA36AF1DD031AEAEA1" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_KratosGovernmentSolutionsMember" xlink:label="loc_ktos_KratosGovernmentSolutionsMember_A046D6A1B6CF9BA6EA771DD031AF5981" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_73B63C6848E4F1FA36AF1DD031AEAEA1" xlink:to="loc_ktos_KratosGovernmentSolutionsMember_A046D6A1B6CF9BA6EA771DD031AF5981" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_KratosUnmannedSystemsMember" xlink:label="loc_ktos_KratosUnmannedSystemsMember_E492AD2634591AE637001DD031AF646E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_73B63C6848E4F1FA36AF1DD031AEAEA1" xlink:to="loc_ktos_KratosUnmannedSystemsMember_E492AD2634591AE637001DD031AF646E" 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_D0DA824F543707A37DB91DD031AFF498" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_5C129FC726F36A99CA061DD031AFE6CF" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_D0DA824F543707A37DB91DD031AFF498" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepreciationDepletionAndAmortizationNonproductionAbstract" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortizationNonproductionAbstract_152519BE85D1FAA764501DD031B00ACD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_5C129FC726F36A99CA061DD031AFE6CF" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortizationNonproductionAbstract_152519BE85D1FAA764501DD031B00ACD" 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_5E91FF1C005F92ED61A91DD031B07D78" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DepreciationDepletionAndAmortizationNonproductionAbstract_152519BE85D1FAA764501DD031B00ACD" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_5E91FF1C005F92ED61A91DD031B07D78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLossAbstract" xlink:label="loc_us-gaap_OperatingIncomeLossAbstract_45D2E22E6874EBC2E5921DD031B0CE0B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_5C129FC726F36A99CA061DD031AFE6CF" xlink:to="loc_us-gaap_OperatingIncomeLossAbstract_45D2E22E6874EBC2E5921DD031B0CE0B" 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_A937157996EC8175138C1DD031B09696" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingIncomeLossAbstract_45D2E22E6874EBC2E5921DD031B0CE0B" xlink:to="loc_us-gaap_OperatingIncomeLoss_A937157996EC8175138C1DD031B09696" 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_0E11079E8694553B94E317087EBBD07B" 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_7A876435165A5B7AA5B857A06373DAA2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_0E11079E8694553B94E317087EBBD07B" xlink:to="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_7A876435165A5B7AA5B857A06373DAA2" 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_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_3F42E645695F53E7A68C2222145712FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_7A876435165A5B7AA5B857A06373DAA2" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_3F42E645695F53E7A68C2222145712FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_DEADC992878E7F467376D8C067D1A43F_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_3F42E645695F53E7A68C2222145712FB" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_DEADC992878E7F467376D8C067D1A43F_DA98DE3F87425575B530E4251D66B5F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_3B1722F6E95E510CB3A24CB9021596E9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_3F42E645695F53E7A68C2222145712FB" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_3B1722F6E95E510CB3A24CB9021596E9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GovernmentContractsConcentrationRiskMember" xlink:label="loc_us-gaap_GovernmentContractsConcentrationRiskMember_C196CAE8184450D194DFE40EBF0743DE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_3B1722F6E95E510CB3A24CB9021596E9" xlink:to="loc_us-gaap_GovernmentContractsConcentrationRiskMember_C196CAE8184450D194DFE40EBF0743DE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_2962C59B72175C139D1743E69D1AA95E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_7A876435165A5B7AA5B857A06373DAA2" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_2962C59B72175C139D1743E69D1AA95E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_F137E40774DF8658B8C2D8C067D17173_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_2962C59B72175C139D1743E69D1AA95E" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_F137E40774DF8658B8C2D8C067D17173_DA98DE3F87425575B530E4251D66B5F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E99007E4FFE15F3FAD75EF99CA19DBF3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_2962C59B72175C139D1743E69D1AA95E" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E99007E4FFE15F3FAD75EF99CA19DBF3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SalesRevenueNetMember" xlink:label="loc_us-gaap_SalesRevenueNetMember_8D582D0561A654FA895849054399FEE4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E99007E4FFE15F3FAD75EF99CA19DBF3" xlink:to="loc_us-gaap_SalesRevenueNetMember_8D582D0561A654FA895849054399FEE4" 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_733AAA25D0E154F7A863806701156EC6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_7A876435165A5B7AA5B857A06373DAA2" xlink:to="loc_srt_MajorCustomersAxis_733AAA25D0E154F7A863806701156EC6" 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_4BC7AF6E05A00F372D4CD8C067D2EB72_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_733AAA25D0E154F7A863806701156EC6" xlink:to="loc_srt_NameOfMajorCustomerDomain_4BC7AF6E05A00F372D4CD8C067D2EB72_DA98DE3F87425575B530E4251D66B5F2" 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_607B13CE8003523C84F2C57A15975116" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_733AAA25D0E154F7A863806701156EC6" xlink:to="loc_srt_NameOfMajorCustomerDomain_607B13CE8003523C84F2C57A15975116" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_USGovernmentMember" xlink:label="loc_ktos_USGovernmentMember_B6ADDE1C672351BB9A73FBF842FA84B5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_607B13CE8003523C84F2C57A15975116" xlink:to="loc_ktos_USGovernmentMember_B6ADDE1C672351BB9A73FBF842FA84B5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_9B78C9888D5B5884B23558457AF20E5C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_0E11079E8694553B94E317087EBBD07B" xlink:to="loc_us-gaap_Revenues_9B78C9888D5B5884B23558457AF20E5C" 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_1073FBBD8B4F5C42B8EB9A3E2C8B30A9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_0E11079E8694553B94E317087EBBD07B" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_1073FBBD8B4F5C42B8EB9A3E2C8B30A9" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SummaryOfSignificantAccountingPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SummaryOfSignificantAccountingPoliciesDetails" 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_7FAC2EFE0594583BA1EECF1BBBE1C516" 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_E9292B7D177F5C4EB5E174C9173423F6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7FAC2EFE0594583BA1EECF1BBBE1C516" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_E9292B7D177F5C4EB5E174C9173423F6" 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_1C57DACF234A510EA51E0052579AD44D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_E9292B7D177F5C4EB5E174C9173423F6" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_1C57DACF234A510EA51E0052579AD44D" 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_DFF990C81417C82BB080D8C065BD515C_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_1C57DACF234A510EA51E0052579AD44D" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DFF990C81417C82BB080D8C065BD515C_DA98DE3F87425575B530E4251D66B5F2" 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_F0B9E24A8A7A5345A6113ED961255CFA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_1C57DACF234A510EA51E0052579AD44D" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_F0B9E24A8A7A5345A6113ED961255CFA" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_FloridaTurbineTechnologiesInc.Member" xlink:label="loc_ktos_FloridaTurbineTechnologiesInc.Member_511DCEAC19935F7583F639DE17F46037" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_F0B9E24A8A7A5345A6113ED961255CFA" xlink:to="loc_ktos_FloridaTurbineTechnologiesInc.Member_511DCEAC19935F7583F639DE17F46037" xlink:type="arc" />
    <link:loc xlink:href="ktos-20190929.xsd#ktos_FTTCoreLLCMember" xlink:label="loc_ktos_FTTCoreLLCMember_F6BB8E509122574CBACEADF10C76C5C7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_F0B9E24A8A7A5345A6113ED961255CFA" xlink:to="loc_ktos_FTTCoreLLCMember_F6BB8E509122574CBACEADF10C76C5C7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidatedEntitiesAxis" xlink:label="loc_srt_ConsolidatedEntitiesAxis_96DE663391225FA1A4E2C9C1BBECDEF4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_E9292B7D177F5C4EB5E174C9173423F6" xlink:to="loc_srt_ConsolidatedEntitiesAxis_96DE663391225FA1A4E2C9C1BBECDEF4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="loc_srt_ConsolidatedEntitiesDomain_6420AC7AF69DB7E79874D8C065BEF80E_DA98DE3F87425575B530E4251D66B5F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_96DE663391225FA1A4E2C9C1BBECDEF4" xlink:to="loc_srt_ConsolidatedEntitiesDomain_6420AC7AF69DB7E79874D8C065BEF80E_DA98DE3F87425575B530E4251D66B5F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="loc_srt_ConsolidatedEntitiesDomain_77F7CED06873511FA3C85D91F7288ACE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_96DE663391225FA1A4E2C9C1BBECDEF4" xlink:to="loc_srt_ConsolidatedEntitiesDomain_77F7CED06873511FA3C85D91F7288ACE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SubsidiariesMember" xlink:label="loc_srt_SubsidiariesMember_F830DF676FC154C39F06F48768DFE5BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_77F7CED06873511FA3C85D91F7288ACE" xlink:to="loc_srt_SubsidiariesMember_F830DF676FC154C39F06F48768DFE5BF" 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_4FFA5F1C461B52308FC4CC5061473483" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7FAC2EFE0594583BA1EECF1BBBE1C516" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_4FFA5F1C461B52308FC4CC5061473483" 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_82FE21C2616F51388B205C0F8E2170E8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7FAC2EFE0594583BA1EECF1BBBE1C516" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_82FE21C2616F51388B205C0F8E2170E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_0B32117982535CCD91FE25EC739BB5D2" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7FAC2EFE0594583BA1EECF1BBBE1C516" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_0B32117982535CCD91FE25EC739BB5D2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.kratosdefense.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="extended" />
</link:linkbase>
