<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2021 Workiva-->
<!--r:c16506e9-0a9c-4375-80cc-5b166a4db132,g:df5d51d1-6d66-43cc-9b44-51b2ad5df643-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/CoverPage" xlink:type="simple" xlink:href="lfus-20201226.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/CoverPage" xlink:type="extended" id="i254624618e6b483a918b4cc78528087f_CoverPage"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/CONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="lfus-20201226.xsd#CONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/CONSOLIDATEDBALANCESHEETS" xlink:type="extended" id="i3a1a3fdaeb1549a1a82fcf5e554327b7_CONSOLIDATEDBALANCESHEETS"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/CONSOLIDATEDBALANCESHEETSParentheticals" xlink:type="simple" xlink:href="lfus-20201226.xsd#CONSOLIDATEDBALANCESHEETSParentheticals"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/CONSOLIDATEDBALANCESHEETSParentheticals" xlink:type="extended" id="i3ba5b6ede9d64a798065c1f1fad1c724_CONSOLIDATEDBALANCESHEETSParentheticals"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/CONSOLIDATEDSTATEMENTSOFNETINCOME" xlink:type="simple" xlink:href="lfus-20201226.xsd#CONSOLIDATEDSTATEMENTSOFNETINCOME"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/CONSOLIDATEDSTATEMENTSOFNETINCOME" xlink:type="extended" id="i5684df6d8db34e76bf15f51979d72be3_CONSOLIDATEDSTATEMENTSOFNETINCOME"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME" xlink:type="simple" xlink:href="lfus-20201226.xsd#CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME" xlink:type="extended" id="i7f027c0910f640339bdff44b4d779f83_CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="simple" xlink:href="lfus-20201226.xsd#CONSOLIDATEDSTATEMENTSOFCASHFLOWS"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="extended" id="i50584e771b9942a2a8404f587c4c2484_CONSOLIDATEDSTATEMENTSOFCASHFLOWS"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/CONSOLIDATEDSTATEMENTSOFEQUITY" xlink:type="simple" xlink:href="lfus-20201226.xsd#CONSOLIDATEDSTATEMENTSOFEQUITY"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/CONSOLIDATEDSTATEMENTSOFEQUITY" xlink:type="extended" id="i7b8dcffa27e348cc87a621edcdf45928_CONSOLIDATEDSTATEMENTSOFEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_87be41fc-a599-45cf-b3ab-6938985e5b03" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_87be41fc-a599-45cf-b3ab-6938985e5b03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_b3ad0bea-4c00-4d32-b2ef-4e388f9e9e0c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_ProfitLoss_b3ad0bea-4c00-4d32-b2ef-4e388f9e9e0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_053d7591-1955-4bd4-9914-81bbea4d3888" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_053d7591-1955-4bd4-9914-81bbea4d3888" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_332e51e7-a4f2-4309-b72f-74edeb361310" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_332e51e7-a4f2-4309-b72f-74edeb361310" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_b3c45216-216d-4742-97b1-e39009295d60" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_b3c45216-216d-4742-97b1-e39009295d60" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_2decf345-7d27-49d5-8333-23a36b3cf416" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_2decf345-7d27-49d5-8333-23a36b3cf416" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_6558a00e-c0f9-44f1-a248-71cba833b6cc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_6558a00e-c0f9-44f1-a248-71cba833b6cc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_612795e7-085a-4fbb-90b5-9d6fd74a903b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_612795e7-085a-4fbb-90b5-9d6fd74a903b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_f61fcecd-a996-4f07-b042-5c53c3df97da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_f61fcecd-a996-4f07-b042-5c53c3df97da" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_7c095316-4077-4ece-b9bb-2db72a55b29d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_DividendsCommonStockCash_7c095316-4077-4ece-b9bb-2db72a55b29d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_5877e337-3e6e-4809-af31-c05aad599fec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_231ada1f-88bb-4dae-8a0b-331a5aa25b70" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_0ea3b29b-5a45-4b91-bbb5-e385ebe91a67" xlink:to="loc_us-gaap_StatementTable_231ada1f-88bb-4dae-8a0b-331a5aa25b70" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_4d49d845-7866-48eb-80d0-9cf9ddc7a5af" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_231ada1f-88bb-4dae-8a0b-331a5aa25b70" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_4d49d845-7866-48eb-80d0-9cf9ddc7a5af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_4d49d845-7866-48eb-80d0-9cf9ddc7a5af_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_4d49d845-7866-48eb-80d0-9cf9ddc7a5af" xlink:to="loc_us-gaap_EquityComponentDomain_4d49d845-7866-48eb-80d0-9cf9ddc7a5af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_3b07e659-4ea8-4efc-bb4d-b418b478035c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_4d49d845-7866-48eb-80d0-9cf9ddc7a5af" xlink:to="loc_us-gaap_EquityComponentDomain_3b07e659-4ea8-4efc-bb4d-b418b478035c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_9688e659-057e-4d80-b115-acb3e9d7c53c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3b07e659-4ea8-4efc-bb4d-b418b478035c" xlink:to="loc_us-gaap_CommonStockMember_9688e659-057e-4d80-b115-acb3e9d7c53c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_ecf33528-173f-45c3-a18a-7d64157a119b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3b07e659-4ea8-4efc-bb4d-b418b478035c" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_ecf33528-173f-45c3-a18a-7d64157a119b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockMember_ae5311a3-86a0-4a67-9fe4-93cfa80df767" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3b07e659-4ea8-4efc-bb4d-b418b478035c" xlink:to="loc_us-gaap_TreasuryStockMember_ae5311a3-86a0-4a67-9fe4-93cfa80df767" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_17c74133-b183-4d7c-adad-6675a7b53740" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3b07e659-4ea8-4efc-bb4d-b418b478035c" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_17c74133-b183-4d7c-adad-6675a7b53740" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_b517764a-2e5e-4ece-92d3-fbf3d105feba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3b07e659-4ea8-4efc-bb4d-b418b478035c" xlink:to="loc_us-gaap_RetainedEarningsMember_b517764a-2e5e-4ece-92d3-fbf3d105feba" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_83d864b4-97c4-4378-9d5d-41104812dedd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3b07e659-4ea8-4efc-bb4d-b418b478035c" xlink:to="loc_us-gaap_NoncontrollingInterestMember_83d864b4-97c4-4378-9d5d-41104812dedd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_4c3d82a2-d3c5-42bd-9607-389647605365" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_231ada1f-88bb-4dae-8a0b-331a5aa25b70" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_4c3d82a2-d3c5-42bd-9607-389647605365" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_4c3d82a2-d3c5-42bd-9607-389647605365_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_4c3d82a2-d3c5-42bd-9607-389647605365" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_4c3d82a2-d3c5-42bd-9607-389647605365_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_5d520c99-2a64-4af5-b843-f0b0f3031e8e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_4c3d82a2-d3c5-42bd-9607-389647605365" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_5d520c99-2a64-4af5-b843-f0b0f3031e8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_efc9a5fe-14bd-4ec3-bc81-95be9d09da2b" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_5d520c99-2a64-4af5-b843-f0b0f3031e8e" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_efc9a5fe-14bd-4ec3-bc81-95be9d09da2b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/CONSOLIDATEDSTATEMENTSOFEQUITYParentheticals" xlink:type="simple" xlink:href="lfus-20201226.xsd#CONSOLIDATEDSTATEMENTSOFEQUITYParentheticals"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/CONSOLIDATEDSTATEMENTSOFEQUITYParentheticals" xlink:type="extended" id="i1ddb043f2ae44e7aaa7a03397f77048f_CONSOLIDATEDSTATEMENTSOFEQUITYParentheticals"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SummaryofSignificantAccountingPoliciesandOtherInformation" xlink:type="simple" xlink:href="lfus-20201226.xsd#SummaryofSignificantAccountingPoliciesandOtherInformation"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SummaryofSignificantAccountingPoliciesandOtherInformation" xlink:type="extended" id="i745221e8155d4e218d5f461da694f759_SummaryofSignificantAccountingPoliciesandOtherInformation"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationPolicies" xlink:type="simple" xlink:href="lfus-20201226.xsd#SummaryofSignificantAccountingPoliciesandOtherInformationPolicies"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationPolicies" xlink:type="extended" id="ibb9984b7e6964b5e9067ad2ce1e6c76e_SummaryofSignificantAccountingPoliciesandOtherInformationPolicies"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#SummaryofSignificantAccountingPoliciesandOtherInformationTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationTables" xlink:type="extended" id="if67b152da715482b8399b5dab314e882_SummaryofSignificantAccountingPoliciesandOtherInformationTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#SummaryofSignificantAccountingPoliciesandOtherInformationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationNarrativeDetails" xlink:type="extended" id="i239d4a00e8e94782bd7cc9c0051f61f2_SummaryofSignificantAccountingPoliciesandOtherInformationNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:href="lfus-20201226.xsd#lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_13fdb298-9d6c-4009-973d-a36db66be321" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_13fdb298-9d6c-4009-973d-a36db66be321" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_7f1177a5-c8f7-4007-8963-c9eeb1f6f68d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_7f1177a5-c8f7-4007-8963-c9eeb1f6f68d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_c8fa2cf7-80bd-447a-a40d-c40d15c82791" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_c8fa2cf7-80bd-447a-a40d-c40d15c82791" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_LongtermInvestmentOwnershipPercentage_8fe6f42a-48b6-41f1-bb2d-8c73e75b74ee" xlink:href="lfus-20201226.xsd#lfus_LongtermInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_lfus_LongtermInvestmentOwnershipPercentage_8fe6f42a-48b6-41f1-bb2d-8c73e75b74ee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNi_c976c35c-1dbc-457f-ae78-a7a450b5424a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_EquitySecuritiesFvNi_c976c35c-1dbc-457f-ae78-a7a450b5424a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_d6cc2888-a5d5-4090-b06a-67cef598f008" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_d6cc2888-a5d5-4090-b06a-67cef598f008" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_5e7829ad-8215-43fa-a12d-a0530d99c528" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_5e7829ad-8215-43fa-a12d-a0530d99c528" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_bb2c6f67-2bf7-4c89-a378-a6b07d7ae933" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_EquityMethodInvestments_bb2c6f67-2bf7-4c89-a378-a6b07d7ae933" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_b5c0ccb9-95a1-48be-a4a8-b471ce4a9373" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_AssetImpairmentCharges_b5c0ccb9-95a1-48be-a4a8-b471ce4a9373" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecurities_dbbfa1eb-7bea-4c48-9d5c-01b0c2d93db3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_MarketableSecurities_dbbfa1eb-7bea-4c48-9d5c-01b0c2d93db3" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_d9ff18a5-8d4b-42b0-a868-7dc884d3ba21" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_d9ff18a5-8d4b-42b0-a868-7dc884d3ba21" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_d3006870-992d-4b28-84b0-37de3d9c89a0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_d3006870-992d-4b28-84b0-37de3d9c89a0" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_c70e6182-1ea0-46a9-aa66-90f0029bd232" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_Goodwill_c70e6182-1ea0-46a9-aa66-90f0029bd232" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportingUnits_39241d2b-87fb-4adb-bbb2-f39b48b31ad6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NumberOfReportingUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_NumberOfReportingUnits_39241d2b-87fb-4adb-bbb2-f39b48b31ad6" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReportingUnitPercentageOfFairValueInExcessOfCarryingAmount_2641c15a-80fe-44ad-97be-4ccf17088aba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReportingUnitPercentageOfFairValueInExcessOfCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_ReportingUnitPercentageOfFairValueInExcessOfCarryingAmount_2641c15a-80fe-44ad-97be-4ccf17088aba" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_742b450b-2c03-4033-a8b3-3724d501d77a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_742b450b-2c03-4033-a8b3-3724d501d77a" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableNoncurrent_84422ffe-28ae-4ed9-8e7a-dcf44bc483e6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableNoncurrent_84422ffe-28ae-4ed9-8e7a-dcf44bc483e6" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdvertisingExpense_8c87fd6f-cbf0-4cb8-ae82-f9b8e54c94f0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdvertisingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_AdvertisingExpense_8c87fd6f-cbf0-4cb8-ae82-f9b8e54c94f0" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_6a1838c5-352d-4a8f-bd4a-1a83438c7497" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_6a1838c5-352d-4a8f-bd4a-1a83438c7497" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualCarryingValueNoncurrent_3c1e5972-ca22-4110-86ff-bedd76e9e111" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingencyAccrualCarryingValueNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_LossContingencyAccrualCarryingValueNoncurrent_3c1e5972-ca22-4110-86ff-bedd76e9e111" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit_7d0eaad2-cf6e-4624-974b-bba4d68ce26c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit_7d0eaad2-cf6e-4624-974b-bba4d68ce26c" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiabilityTollChargeNoncurrent_f11c406c-d409-41d6-bb86-376e6d5f17ec" xlink:href="lfus-20201226.xsd#lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiabilityTollChargeNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiabilityTollChargeNoncurrent_f11c406c-d409-41d6-bb86-376e6d5f17ec" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentofDeferredTaxAssetLiabilityTollChargeCurrent_298b8845-ee1b-4287-9037-428b00e1c578" xlink:href="lfus-20201226.xsd#lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentofDeferredTaxAssetLiabilityTollChargeCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentofDeferredTaxAssetLiabilityTollChargeCurrent_298b8845-ee1b-4287-9037-428b00e1c578" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:href="lfus-20201226.xsd#lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationLineItems_1178cd12-ffeb-48e3-b167-e7a983f11bd1" xlink:to="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_55e998b6-31c1-42c3-ac99-8244f2ab122f" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RestatementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_srt_RestatementAxis_55e998b6-31c1-42c3-ac99-8244f2ab122f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_55e998b6-31c1-42c3-ac99-8244f2ab122f_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_55e998b6-31c1-42c3-ac99-8244f2ab122f" xlink:to="loc_srt_RestatementDomain_55e998b6-31c1-42c3-ac99-8244f2ab122f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_9875cfe4-85c5-47ed-9e1b-46f51c9cefab" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_55e998b6-31c1-42c3-ac99-8244f2ab122f" xlink:to="loc_srt_RestatementDomain_9875cfe4-85c5-47ed-9e1b-46f51c9cefab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAdjustmentMember_1f43a463-397c-49ab-96fd-de0afb9522c4" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RestatementAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_9875cfe4-85c5-47ed-9e1b-46f51c9cefab" xlink:to="loc_srt_RestatementAdjustmentMember_1f43a463-397c-49ab-96fd-de0afb9522c4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_f0aa92df-6e0d-4a01-9db0-de70e3700415" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_f0aa92df-6e0d-4a01-9db0-de70e3700415" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f0aa92df-6e0d-4a01-9db0-de70e3700415_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_f0aa92df-6e0d-4a01-9db0-de70e3700415" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f0aa92df-6e0d-4a01-9db0-de70e3700415_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ae0a0104-73ff-4f61-a60e-7ffa8796cb5e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_f0aa92df-6e0d-4a01-9db0-de70e3700415" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ae0a0104-73ff-4f61-a60e-7ffa8796cb5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IXYSCorporationMember_c5793c64-bdc9-4c5f-a72b-cda815a7299d" xlink:href="lfus-20201226.xsd#lfus_IXYSCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ae0a0104-73ff-4f61-a60e-7ffa8796cb5e" xlink:to="loc_lfus_IXYSCorporationMember_c5793c64-bdc9-4c5f-a72b-cda815a7299d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodAxis_90b264a2-ce4e-4f4e-9dcc-bd0de38f1a75" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_us-gaap_TaxPeriodAxis_90b264a2-ce4e-4f4e-9dcc-bd0de38f1a75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_90b264a2-ce4e-4f4e-9dcc-bd0de38f1a75_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TaxPeriodAxis_90b264a2-ce4e-4f4e-9dcc-bd0de38f1a75" xlink:to="loc_us-gaap_TaxPeriodDomain_90b264a2-ce4e-4f4e-9dcc-bd0de38f1a75_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_40b5cc8b-187b-4232-877c-fde2f2f37551" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TaxPeriodAxis_90b264a2-ce4e-4f4e-9dcc-bd0de38f1a75" xlink:to="loc_us-gaap_TaxPeriodDomain_40b5cc8b-187b-4232-877c-fde2f2f37551" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_TollChargeMember_0f049744-51e4-4ecc-94a0-db677b299ee4" xlink:href="lfus-20201226.xsd#lfus_TollChargeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxPeriodDomain_40b5cc8b-187b-4232-877c-fde2f2f37551" xlink:to="loc_lfus_TollChargeMember_0f049744-51e4-4ecc-94a0-db677b299ee4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_OtherItemsMember_85a4f28e-6ef1-4bd4-a7b5-c813fb343b95" xlink:href="lfus-20201226.xsd#lfus_OtherItemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxPeriodDomain_40b5cc8b-187b-4232-877c-fde2f2f37551" xlink:to="loc_lfus_OtherItemsMember_85a4f28e-6ef1-4bd4-a7b5-c813fb343b95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_78089643-cf87-43b6-81dc-0c3640614cf5" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_78089643-cf87-43b6-81dc-0c3640614cf5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_78089643-cf87-43b6-81dc-0c3640614cf5_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_78089643-cf87-43b6-81dc-0c3640614cf5" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_78089643-cf87-43b6-81dc-0c3640614cf5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_2f13b2d2-0354-4ede-889d-3f6c19ecc3c5" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_78089643-cf87-43b6-81dc-0c3640614cf5" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_2f13b2d2-0354-4ede-889d-3f6c19ecc3c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_PolytronicsMember_834c0624-e218-4987-9af0-6a69f2d64db9" xlink:href="lfus-20201226.xsd#lfus_PolytronicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_2f13b2d2-0354-4ede-889d-3f6c19ecc3c5" xlink:to="loc_lfus_PolytronicsMember_834c0624-e218-4987-9af0-6a69f2d64db9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_PowersemMember_b372a7ff-1391-47f8-beca-cb168336be3b" xlink:href="lfus-20201226.xsd#lfus_PowersemMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_2f13b2d2-0354-4ede-889d-3f6c19ecc3c5" xlink:to="loc_lfus_PowersemMember_b372a7ff-1391-47f8-beca-cb168336be3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_EBTechMember_18eb6e13-f616-4928-a92f-d6b4437c7cfd" xlink:href="lfus-20201226.xsd#lfus_EBTechMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_2f13b2d2-0354-4ede-889d-3f6c19ecc3c5" xlink:to="loc_lfus_EBTechMember_18eb6e13-f616-4928-a92f-d6b4437c7cfd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ATECMember_89c20b03-b948-4073-81f8-32637de5b402" xlink:href="lfus-20201226.xsd#lfus_ATECMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_2f13b2d2-0354-4ede-889d-3f6c19ecc3c5" xlink:to="loc_lfus_ATECMember_89c20b03-b948-4073-81f8-32637de5b402" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_2ad59768-6020-4a7a-b509-557a96f596c2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_2ad59768-6020-4a7a-b509-557a96f596c2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_2ad59768-6020-4a7a-b509-557a96f596c2_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_2ad59768-6020-4a7a-b509-557a96f596c2" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_2ad59768-6020-4a7a-b509-557a96f596c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_ee039e89-0478-4838-81f9-6e8fd0244271" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_2ad59768-6020-4a7a-b509-557a96f596c2" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_ee039e89-0478-4838-81f9-6e8fd0244271" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncurrentAssetsMember_33c2ea0f-d62f-4564-990f-9a55c85d555e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherNoncurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_ee039e89-0478-4838-81f9-6e8fd0244271" xlink:to="loc_us-gaap_OtherNoncurrentAssetsMember_33c2ea0f-d62f-4564-990f-9a55c85d555e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMember_e116a6c8-0948-43d1-a57b-186cfc7acec8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_ee039e89-0478-4838-81f9-6e8fd0244271" xlink:to="loc_us-gaap_OtherAssetsMember_e116a6c8-0948-43d1-a57b-186cfc7acec8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_66e98f04-dff8-40f5-b98e-fe2ee04e8f5a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_66e98f04-dff8-40f5-b98e-fe2ee04e8f5a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_66e98f04-dff8-40f5-b98e-fe2ee04e8f5a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_66e98f04-dff8-40f5-b98e-fe2ee04e8f5a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_66e98f04-dff8-40f5-b98e-fe2ee04e8f5a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b4737b60-b54a-4fdb-b8ac-7eeda7cf4ddd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_66e98f04-dff8-40f5-b98e-fe2ee04e8f5a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b4737b60-b54a-4fdb-b8ac-7eeda7cf4ddd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingMember_48638a93-2fa2-4b1b-96ed-e428f2f85169" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b4737b60-b54a-4fdb-b8ac-7eeda7cf4ddd" xlink:to="loc_us-gaap_BuildingMember_48638a93-2fa2-4b1b-96ed-e428f2f85169" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquipmentMember_6f2ee8c5-fcc3-4ca3-8f7c-b7c24090bf0c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b4737b60-b54a-4fdb-b8ac-7eeda7cf4ddd" xlink:to="loc_us-gaap_EquipmentMember_6f2ee8c5-fcc3-4ca3-8f7c-b7c24090bf0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_8f1b5ddf-8706-4949-b5bc-a3308d5eaeb6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b4737b60-b54a-4fdb-b8ac-7eeda7cf4ddd" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_8f1b5ddf-8706-4949-b5bc-a3308d5eaeb6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ToolsDiesAndMoldsMember_7247994e-1cdc-4b08-adde-ab67ffe12201" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ToolsDiesAndMoldsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b4737b60-b54a-4fdb-b8ac-7eeda7cf4ddd" xlink:to="loc_us-gaap_ToolsDiesAndMoldsMember_7247994e-1cdc-4b08-adde-ab67ffe12201" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_0a3396d9-9445-44f8-b719-ede96a9b7500" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComputerEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b4737b60-b54a-4fdb-b8ac-7eeda7cf4ddd" xlink:to="loc_us-gaap_ComputerEquipmentMember_0a3396d9-9445-44f8-b719-ede96a9b7500" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_4cfd7a31-0a98-49b0-bc4c-5e8048a8f8c3" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_srt_RangeAxis_4cfd7a31-0a98-49b0-bc4c-5e8048a8f8c3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_4cfd7a31-0a98-49b0-bc4c-5e8048a8f8c3_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_4cfd7a31-0a98-49b0-bc4c-5e8048a8f8c3" xlink:to="loc_srt_RangeMember_4cfd7a31-0a98-49b0-bc4c-5e8048a8f8c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_351efa1a-478b-489b-ae21-9dacadc16159" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_4cfd7a31-0a98-49b0-bc4c-5e8048a8f8c3" xlink:to="loc_srt_RangeMember_351efa1a-478b-489b-ae21-9dacadc16159" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_f6572616-8d79-4c71-904d-ef30a95d6725" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_351efa1a-478b-489b-ae21-9dacadc16159" xlink:to="loc_srt_MinimumMember_f6572616-8d79-4c71-904d-ef30a95d6725" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_27537618-f230-41f1-a3c8-eac6b2c61373" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_351efa1a-478b-489b-ae21-9dacadc16159" xlink:to="loc_srt_MaximumMember_27537618-f230-41f1-a3c8-eac6b2c61373" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReportingUnitAxis_377e2163-9a2e-4427-809e-30ac8129b889" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReportingUnitAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_us-gaap_ReportingUnitAxis_377e2163-9a2e-4427-809e-30ac8129b889" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReportingUnitDomain_377e2163-9a2e-4427-809e-30ac8129b889_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReportingUnitDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReportingUnitAxis_377e2163-9a2e-4427-809e-30ac8129b889" xlink:to="loc_us-gaap_ReportingUnitDomain_377e2163-9a2e-4427-809e-30ac8129b889_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReportingUnitDomain_698934a0-1686-4d3b-8b45-3a7405446852" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReportingUnitDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReportingUnitAxis_377e2163-9a2e-4427-809e-30ac8129b889" xlink:to="loc_us-gaap_ReportingUnitDomain_698934a0-1686-4d3b-8b45-3a7405446852" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ElectronicsNonSiliconUnitMember_41e34df5-6c97-4e92-a31f-30a8fa78ee07" xlink:href="lfus-20201226.xsd#lfus_ElectronicsNonSiliconUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReportingUnitDomain_698934a0-1686-4d3b-8b45-3a7405446852" xlink:to="loc_lfus_ElectronicsNonSiliconUnitMember_41e34df5-6c97-4e92-a31f-30a8fa78ee07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ElectronicsSiliconUnitMember_c921120d-d7f2-4388-b635-f473d69d39b5" xlink:href="lfus-20201226.xsd#lfus_ElectronicsSiliconUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReportingUnitDomain_698934a0-1686-4d3b-8b45-3a7405446852" xlink:to="loc_lfus_ElectronicsSiliconUnitMember_c921120d-d7f2-4388-b635-f473d69d39b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_PassengerCarMember_361f1baf-a181-41dc-a14d-3c67136b979a" xlink:href="lfus-20201226.xsd#lfus_PassengerCarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReportingUnitDomain_698934a0-1686-4d3b-8b45-3a7405446852" xlink:to="loc_lfus_PassengerCarMember_361f1baf-a181-41dc-a14d-3c67136b979a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_CommercialVehicleProductsMember_96f44052-5343-47dd-8bd2-b69f2bc765df" xlink:href="lfus-20201226.xsd#lfus_CommercialVehicleProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReportingUnitDomain_698934a0-1686-4d3b-8b45-3a7405446852" xlink:to="loc_lfus_CommercialVehicleProductsMember_96f44052-5343-47dd-8bd2-b69f2bc765df" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AutomotiveSensorsMember_99856f13-228f-49a2-9e71-a3d6682ee5f4" xlink:href="lfus-20201226.xsd#lfus_AutomotiveSensorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReportingUnitDomain_698934a0-1686-4d3b-8b45-3a7405446852" xlink:to="loc_lfus_AutomotiveSensorsMember_99856f13-228f-49a2-9e71-a3d6682ee5f4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_SensorsMember_6db22ec2-0756-4064-b85c-04bc086cb793" xlink:href="lfus-20201226.xsd#lfus_SensorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReportingUnitDomain_698934a0-1686-4d3b-8b45-3a7405446852" xlink:to="loc_lfus_SensorsMember_6db22ec2-0756-4064-b85c-04bc086cb793" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_RelayUnitMember_178eb726-44be-4714-9026-aeed037ecb98" xlink:href="lfus-20201226.xsd#lfus_RelayUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReportingUnitDomain_698934a0-1686-4d3b-8b45-3a7405446852" xlink:to="loc_lfus_RelayUnitMember_178eb726-44be-4714-9026-aeed037ecb98" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_FuseUnitMember_04906966-664f-4949-84d2-0d2d953cd8e4" xlink:href="lfus-20201226.xsd#lfus_FuseUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReportingUnitDomain_698934a0-1686-4d3b-8b45-3a7405446852" xlink:to="loc_lfus_FuseUnitMember_04906966-664f-4949-84d2-0d2d953cd8e4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e267bde5-29e2-49db-8d38-b595fc2f7aee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e267bde5-29e2-49db-8d38-b595fc2f7aee" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e267bde5-29e2-49db-8d38-b595fc2f7aee_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e267bde5-29e2-49db-8d38-b595fc2f7aee" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e267bde5-29e2-49db-8d38-b595fc2f7aee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1bd48111-f4ac-4c58-aec0-7c572d01d7a3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e267bde5-29e2-49db-8d38-b595fc2f7aee" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1bd48111-f4ac-4c58-aec0-7c572d01d7a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_dae93ac7-816b-42b5-9f22-ebb286d35a53" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1bd48111-f4ac-4c58-aec0-7c572d01d7a3" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_dae93ac7-816b-42b5-9f22-ebb286d35a53" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_PatentsLicensesAndSoftwareMember_1f5f95fa-509a-4aaf-bdac-574bd565e0d7" xlink:href="lfus-20201226.xsd#lfus_PatentsLicensesAndSoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1bd48111-f4ac-4c58-aec0-7c572d01d7a3" xlink:to="loc_lfus_PatentsLicensesAndSoftwareMember_1f5f95fa-509a-4aaf-bdac-574bd565e0d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DistributionRightsMember_53fcf09d-e538-46c4-89ac-ae271940de4f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DistributionRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1bd48111-f4ac-4c58-aec0-7c572d01d7a3" xlink:to="loc_us-gaap_DistributionRightsMember_53fcf09d-e538-46c4-89ac-ae271940de4f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UseRightsMember_c6b94350-797b-44f3-9d5d-7553ef9f91d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UseRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1bd48111-f4ac-4c58-aec0-7c572d01d7a3" xlink:to="loc_us-gaap_UseRightsMember_c6b94350-797b-44f3-9d5d-7553ef9f91d2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_5dfb980a-f157-4dfb-8be7-2827f9aaef4b" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_srt_ProductOrServiceAxis_5dfb980a-f157-4dfb-8be7-2827f9aaef4b" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_5dfb980a-f157-4dfb-8be7-2827f9aaef4b_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_5dfb980a-f157-4dfb-8be7-2827f9aaef4b" xlink:to="loc_srt_ProductsAndServicesDomain_5dfb980a-f157-4dfb-8be7-2827f9aaef4b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_5bdc7a8d-5da7-4791-a0f7-31be0f06f1b8" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_5dfb980a-f157-4dfb-8be7-2827f9aaef4b" xlink:to="loc_srt_ProductsAndServicesDomain_5bdc7a8d-5da7-4791-a0f7-31be0f06f1b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShippingAndHandlingMember_897cacfb-a996-4848-b979-160f1405bdda" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShippingAndHandlingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_5bdc7a8d-5da7-4791-a0f7-31be0f06f1b8" xlink:to="loc_us-gaap_ShippingAndHandlingMember_897cacfb-a996-4848-b979-160f1405bdda" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f461a41a-d89e-4fae-b0ae-74e9c8822b09" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f461a41a-d89e-4fae-b0ae-74e9c8822b09" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_f461a41a-d89e-4fae-b0ae-74e9c8822b09_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f461a41a-d89e-4fae-b0ae-74e9c8822b09" xlink:to="loc_us-gaap_RelatedPartyDomain_f461a41a-d89e-4fae-b0ae-74e9c8822b09_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_b8d7e901-e64f-407d-8fd2-a11650425a3b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f461a41a-d89e-4fae-b0ae-74e9c8822b09" xlink:to="loc_us-gaap_RelatedPartyDomain_b8d7e901-e64f-407d-8fd2-a11650425a3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_03170e67-979a-498b-9f9f-d3b301da2f1e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvesteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_b8d7e901-e64f-407d-8fd2-a11650425a3b" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_03170e67-979a-498b-9f9f-d3b301da2f1e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_61f6c644-e3e1-4589-a5e3-6d0b26bd909d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_61f6c644-e3e1-4589-a5e3-6d0b26bd909d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_61f6c644-e3e1-4589-a5e3-6d0b26bd909d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_61f6c644-e3e1-4589-a5e3-6d0b26bd909d" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_61f6c644-e3e1-4589-a5e3-6d0b26bd909d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_2af11a2b-faa3-4546-a9ee-1344444c73a3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_61f6c644-e3e1-4589-a5e3-6d0b26bd909d" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_2af11a2b-faa3-4546-a9ee-1344444c73a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_OtherExpenseIncomeMember_164fbfc9-f069-488c-85d7-73c9f725e28e" xlink:href="lfus-20201226.xsd#lfus_OtherExpenseIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_2af11a2b-faa3-4546-a9ee-1344444c73a3" xlink:to="loc_lfus_OtherExpenseIncomeMember_164fbfc9-f069-488c-85d7-73c9f725e28e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_4621cdf7-2bc7-4c80-bf78-b395ed81f8f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_2af11a2b-faa3-4546-a9ee-1344444c73a3" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_4621cdf7-2bc7-4c80-bf78-b395ed81f8f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_502eb269-e69d-4ddc-a70a-8593b2156301" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_lfus_SummaryofSignificantAccountingPoliciesandOtherInformationTable_a24f14e6-3fce-4e6d-b664-b1218d3e82e2" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_502eb269-e69d-4ddc-a70a-8593b2156301" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_502eb269-e69d-4ddc-a70a-8593b2156301_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_502eb269-e69d-4ddc-a70a-8593b2156301" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_502eb269-e69d-4ddc-a70a-8593b2156301_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_02f29ca5-e067-4564-a9a6-11da59f04b45" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_502eb269-e69d-4ddc-a70a-8593b2156301" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_02f29ca5-e067-4564-a9a6-11da59f04b45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_b7df3e57-6a9c-4844-bd80-e1a3104750bc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_02f29ca5-e067-4564-a9a6-11da59f04b45" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_b7df3e57-6a9c-4844-bd80-e1a3104750bc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationRevenueDisaggregationDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#SummaryofSignificantAccountingPoliciesandOtherInformationRevenueDisaggregationDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationRevenueDisaggregationDetails" xlink:type="extended" id="ia3016ef2f4a44466b426b37220b10f4b_SummaryofSignificantAccountingPoliciesandOtherInformationRevenueDisaggregationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_c96de742-23bb-478d-b15d-441f00636041" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_b5ef5fb8-d339-473c-af7c-cd7dd32675f8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_c96de742-23bb-478d-b15d-441f00636041" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_b5ef5fb8-d339-473c-af7c-cd7dd32675f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_add3e65b-5c2f-43a1-93a7-c8a3a4ab3128" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_c96de742-23bb-478d-b15d-441f00636041" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_add3e65b-5c2f-43a1-93a7-c8a3a4ab3128" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_812d4a0d-bda1-4343-8447-b380fc462287" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_add3e65b-5c2f-43a1-93a7-c8a3a4ab3128" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_812d4a0d-bda1-4343-8447-b380fc462287" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_812d4a0d-bda1-4343-8447-b380fc462287_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_812d4a0d-bda1-4343-8447-b380fc462287" xlink:to="loc_us-gaap_SegmentDomain_812d4a0d-bda1-4343-8447-b380fc462287_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_5684ae81-07a7-44d0-b481-ded241d1d70e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_812d4a0d-bda1-4343-8447-b380fc462287" xlink:to="loc_us-gaap_SegmentDomain_5684ae81-07a7-44d0-b481-ded241d1d70e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ElectronicsMember_5c473627-7793-4207-905e-998f0960e3ac" xlink:href="lfus-20201226.xsd#lfus_ElectronicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5684ae81-07a7-44d0-b481-ded241d1d70e" xlink:to="loc_lfus_ElectronicsMember_5c473627-7793-4207-905e-998f0960e3ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AutomotiveMember_53ef1460-e4b2-4c23-b889-eb32925b8443" xlink:href="lfus-20201226.xsd#lfus_AutomotiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5684ae81-07a7-44d0-b481-ded241d1d70e" xlink:to="loc_lfus_AutomotiveMember_53ef1460-e4b2-4c23-b889-eb32925b8443" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IndustrialMember_e331ad0e-3af1-417e-97d7-2ebbec191f64" xlink:href="lfus-20201226.xsd#lfus_IndustrialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5684ae81-07a7-44d0-b481-ded241d1d70e" xlink:to="loc_lfus_IndustrialMember_e331ad0e-3af1-417e-97d7-2ebbec191f64" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_fdd776af-1307-4f30-998a-016821867057" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_add3e65b-5c2f-43a1-93a7-c8a3a4ab3128" xlink:to="loc_srt_ProductOrServiceAxis_fdd776af-1307-4f30-998a-016821867057" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_fdd776af-1307-4f30-998a-016821867057_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_fdd776af-1307-4f30-998a-016821867057" xlink:to="loc_srt_ProductsAndServicesDomain_fdd776af-1307-4f30-998a-016821867057_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_ced0af2a-fa6e-460a-a65e-4fe634ff1e4e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_fdd776af-1307-4f30-998a-016821867057" xlink:to="loc_srt_ProductsAndServicesDomain_ced0af2a-fa6e-460a-a65e-4fe634ff1e4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ElectronicsSemiconductorMember_aa46a12e-f165-4652-92cf-5b62fddd6797" xlink:href="lfus-20201226.xsd#lfus_ElectronicsSemiconductorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_ced0af2a-fa6e-460a-a65e-4fe634ff1e4e" xlink:to="loc_lfus_ElectronicsSemiconductorMember_aa46a12e-f165-4652-92cf-5b62fddd6797" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ElectronicsPassiveProductsAndSensorsMember_dac4d581-4279-456e-a9b1-f4d46fb1502c" xlink:href="lfus-20201226.xsd#lfus_ElectronicsPassiveProductsAndSensorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_ced0af2a-fa6e-460a-a65e-4fe634ff1e4e" xlink:to="loc_lfus_ElectronicsPassiveProductsAndSensorsMember_dac4d581-4279-456e-a9b1-f4d46fb1502c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_PassengerCarProductsMember_921d0b3d-f82a-4e30-9c3d-69faea774d4d" xlink:href="lfus-20201226.xsd#lfus_PassengerCarProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_ced0af2a-fa6e-460a-a65e-4fe634ff1e4e" xlink:to="loc_lfus_PassengerCarProductsMember_921d0b3d-f82a-4e30-9c3d-69faea774d4d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_CommercialVehicleProductsMember_184dd484-aaae-4d63-8019-a6768eb39341" xlink:href="lfus-20201226.xsd#lfus_CommercialVehicleProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_ced0af2a-fa6e-460a-a65e-4fe634ff1e4e" xlink:to="loc_lfus_CommercialVehicleProductsMember_184dd484-aaae-4d63-8019-a6768eb39341" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AutomotiveSensorsMember_794da27f-b68f-4291-8710-f4bc05c3e977" xlink:href="lfus-20201226.xsd#lfus_AutomotiveSensorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_ced0af2a-fa6e-460a-a65e-4fe634ff1e4e" xlink:to="loc_lfus_AutomotiveSensorsMember_794da27f-b68f-4291-8710-f4bc05c3e977" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IndustrialProductsMember_8ac4a31c-cdca-4399-b2bf-7f8c36cbee62" xlink:href="lfus-20201226.xsd#lfus_IndustrialProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_ced0af2a-fa6e-460a-a65e-4fe634ff1e4e" xlink:to="loc_lfus_IndustrialProductsMember_8ac4a31c-cdca-4399-b2bf-7f8c36cbee62" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/Acquisitions" xlink:type="simple" xlink:href="lfus-20201226.xsd#Acquisitions"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/Acquisitions" xlink:type="extended" id="i6c784b57759144959cf19ee7d8f7a562_Acquisitions"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/AcquisitionsTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#AcquisitionsTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/AcquisitionsTables" xlink:type="extended" id="i5a3795d0ecc94e65b553642687dc50a3_AcquisitionsTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/AcquisitionsNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#AcquisitionsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/AcquisitionsNarrativeDetails" xlink:type="extended" id="i3dca729ffb0a402786ad869b0912f4fc_AcquisitionsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_NumberofCustomers_5d24e3de-6973-4c0c-ac5b-041b241fb037" xlink:href="lfus-20201226.xsd#lfus_NumberofCustomers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_lfus_NumberofCustomers_5d24e3de-6973-4c0c-ac5b-041b241fb037" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_67bc94a2-67a3-4a16-9f67-d2ea35197acf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_67bc94a2-67a3-4a16-9f67-d2ea35197acf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionSharePrice_8f1242a8-bd2f-42a2-b4fe-ffed84d37be2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionSharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_BusinessAcquisitionSharePrice_8f1242a8-bd2f-42a2-b4fe-ffed84d37be2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_BusinessAcquisitionShareExchangeRatio_60761359-36cf-48fc-9e8d-1b92b789f009" xlink:href="lfus-20201226.xsd#lfus_BusinessAcquisitionShareExchangeRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_lfus_BusinessAcquisitionShareExchangeRatio_60761359-36cf-48fc-9e8d-1b92b789f009" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_6fb14f75-e686-43ba-8412-a9d62a81898e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_SharePrice_6fb14f75-e686-43ba-8412-a9d62a81898e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_BusinessCombinationConsiderationTransferredExcludingValueOfStockOptionsConverted_c12ed297-d664-4c1a-baa7-a8f38f7f646f" xlink:href="lfus-20201226.xsd#lfus_BusinessCombinationConsiderationTransferredExcludingValueOfStockOptionsConverted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_lfus_BusinessCombinationConsiderationTransferredExcludingValueOfStockOptionsConverted_c12ed297-d664-4c1a-baa7-a8f38f7f646f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_54a81be5-449d-4d74-88ea-3e10a0c53781" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_54a81be5-449d-4d74-88ea-3e10a0c53781" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_3a8992f9-634a-41d2-9648-0e33ccbd9675" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_3a8992f9-634a-41d2-9648-0e33ccbd9675" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_BusinessCombinationValueOfStockOptionsConvertedToCompanysStockOptions_aa1d9364-9c89-4a5d-b66e-91ebca81b89e" xlink:href="lfus-20201226.xsd#lfus_BusinessCombinationValueOfStockOptionsConvertedToCompanysStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_lfus_BusinessCombinationValueOfStockOptionsConvertedToCompanysStockOptions_aa1d9364-9c89-4a5d-b66e-91ebca81b89e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_ccc20de8-4b36-40c2-bd05-be371e7a55c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_ccc20de8-4b36-40c2-bd05-be371e7a55c5" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_c1f24e05-18d2-4969-885f-0e5e8f3f7cc3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_c1f24e05-18d2-4969-885f-0e5e8f3f7cc3" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit_438e68cc-6b55-43ee-8563-31ee94163b53" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit_438e68cc-6b55-43ee-8563-31ee94163b53" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_da3e6450-1a53-4d6d-a71e-83a7e8a5dce7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_da3e6450-1a53-4d6d-a71e-83a7e8a5dce7" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_5d4cb48b-f3f2-42e1-9da4-27abbab212e7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_5d4cb48b-f3f2-42e1-9da4-27abbab212e7" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_0a8780b1-0b39-4f62-a5b0-873694d35d2e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_0a8780b1-0b39-4f62-a5b0-873694d35d2e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_f2faf615-895f-47eb-8cbf-e77d60022228" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_f2faf615-895f-47eb-8cbf-e77d60022228" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_06db9437-8ac0-4692-9b32-09ebc85eb8a3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_ShareBasedCompensation_06db9437-8ac0-4692-9b32-09ebc85eb8a3" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory_38e8da4d-2674-4dc4-b9ad-f43ad621aaf1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory_38e8da4d-2674-4dc4-b9ad-f43ad621aaf1" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_62ddffb3-ddaa-420c-980a-1e95505abf49" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_62ddffb3-ddaa-420c-980a-1e95505abf49" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_6813c7c3-43a7-4c87-a44a-cf97d022be8f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_6813c7c3-43a7-4c87-a44a-cf97d022be8f" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_InventoryAmortizationPeriod_f711de59-9c9f-419f-aec0-c266ce0ef1ee" xlink:href="lfus-20201226.xsd#lfus_InventoryAmortizationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_lfus_InventoryAmortizationPeriod_f711de59-9c9f-419f-aec0-c266ce0ef1ee" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_84b523fe-a1d4-4c27-a09b-3169908d857e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a08fb3eb-8a2a-4c68-a023-f3b66699fd33" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_84b523fe-a1d4-4c27-a09b-3169908d857e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_f0163fca-c927-4786-bbb4-53742d20214d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_84b523fe-a1d4-4c27-a09b-3169908d857e" xlink:to="loc_us-gaap_AwardTypeAxis_f0163fca-c927-4786-bbb4-53742d20214d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f0163fca-c927-4786-bbb4-53742d20214d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_f0163fca-c927-4786-bbb4-53742d20214d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f0163fca-c927-4786-bbb4-53742d20214d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ffeeb238-c379-4533-807d-b7d54acb3a10" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_f0163fca-c927-4786-bbb4-53742d20214d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ffeeb238-c379-4533-807d-b7d54acb3a10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_98bc46e6-69d5-4646-b1d8-ac7476c8e133" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ffeeb238-c379-4533-807d-b7d54acb3a10" xlink:to="loc_us-gaap_EmployeeStockOptionMember_98bc46e6-69d5-4646-b1d8-ac7476c8e133" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodAxis_bf69aac0-3001-4bd5-bce6-d5b7996317c0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_84b523fe-a1d4-4c27-a09b-3169908d857e" xlink:to="loc_us-gaap_TaxPeriodAxis_bf69aac0-3001-4bd5-bce6-d5b7996317c0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_bf69aac0-3001-4bd5-bce6-d5b7996317c0_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TaxPeriodAxis_bf69aac0-3001-4bd5-bce6-d5b7996317c0" xlink:to="loc_us-gaap_TaxPeriodDomain_bf69aac0-3001-4bd5-bce6-d5b7996317c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_7fa2342e-eca2-4929-b1a1-cc6f7cf9a6ad" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TaxPeriodAxis_bf69aac0-3001-4bd5-bce6-d5b7996317c0" xlink:to="loc_us-gaap_TaxPeriodDomain_7fa2342e-eca2-4929-b1a1-cc6f7cf9a6ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_TollChargeMember_bb5a9f09-b4ee-45fb-9a8b-47fd062c5603" xlink:href="lfus-20201226.xsd#lfus_TollChargeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxPeriodDomain_7fa2342e-eca2-4929-b1a1-cc6f7cf9a6ad" xlink:to="loc_lfus_TollChargeMember_bb5a9f09-b4ee-45fb-9a8b-47fd062c5603" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_9f66e860-e0d6-4150-aa1d-614c3f770565" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_84b523fe-a1d4-4c27-a09b-3169908d857e" xlink:to="loc_dei_LegalEntityAxis_9f66e860-e0d6-4150-aa1d-614c3f770565" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_9f66e860-e0d6-4150-aa1d-614c3f770565_default" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_9f66e860-e0d6-4150-aa1d-614c3f770565" xlink:to="loc_dei_EntityDomain_9f66e860-e0d6-4150-aa1d-614c3f770565_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_85c30e7c-6b89-482a-975b-606c6f7c6ca7" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_9f66e860-e0d6-4150-aa1d-614c3f770565" xlink:to="loc_dei_EntityDomain_85c30e7c-6b89-482a-975b-606c6f7c6ca7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IXYSCorporationMember_cf2757c9-9189-4203-a54e-4a28dd1d67be" xlink:href="lfus-20201226.xsd#lfus_IXYSCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_85c30e7c-6b89-482a-975b-606c6f7c6ca7" xlink:to="loc_lfus_IXYSCorporationMember_cf2757c9-9189-4203-a54e-4a28dd1d67be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_50a37bd8-557e-421d-b088-ad7a8dea05a0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_84b523fe-a1d4-4c27-a09b-3169908d857e" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_50a37bd8-557e-421d-b088-ad7a8dea05a0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_50a37bd8-557e-421d-b088-ad7a8dea05a0_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_50a37bd8-557e-421d-b088-ad7a8dea05a0" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_50a37bd8-557e-421d-b088-ad7a8dea05a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6a630a9-d912-4f32-8832-e5a428759dbb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_50a37bd8-557e-421d-b088-ad7a8dea05a0" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6a630a9-d912-4f32-8832-e5a428759dbb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IXYSCorporationMember_fad18f84-3d38-4751-8a45-2a2dd5bd193f" xlink:href="lfus-20201226.xsd#lfus_IXYSCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6a630a9-d912-4f32-8832-e5a428759dbb" xlink:to="loc_lfus_IXYSCorporationMember_fad18f84-3d38-4751-8a45-2a2dd5bd193f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_51aef17f-c615-47f8-b491-86c9a7ab18c1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_84b523fe-a1d4-4c27-a09b-3169908d857e" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_51aef17f-c615-47f8-b491-86c9a7ab18c1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_51aef17f-c615-47f8-b491-86c9a7ab18c1_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_51aef17f-c615-47f8-b491-86c9a7ab18c1" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_51aef17f-c615-47f8-b491-86c9a7ab18c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_6e55b233-f59d-492a-b5dc-bc9b66872a7d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_51aef17f-c615-47f8-b491-86c9a7ab18c1" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_6e55b233-f59d-492a-b5dc-bc9b66872a7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_01b7d567-3dd5-456f-8556-30c75a5b094f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_6e55b233-f59d-492a-b5dc-bc9b66872a7d" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_01b7d567-3dd5-456f-8556-30c75a5b094f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b5275e7d-a362-4ef0-a6be-d4f74391a317" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_84b523fe-a1d4-4c27-a09b-3169908d857e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b5275e7d-a362-4ef0-a6be-d4f74391a317" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b5275e7d-a362-4ef0-a6be-d4f74391a317_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b5275e7d-a362-4ef0-a6be-d4f74391a317" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b5275e7d-a362-4ef0-a6be-d4f74391a317_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1ddf465a-3a81-4419-8272-c4c079ac4fb1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b5275e7d-a362-4ef0-a6be-d4f74391a317" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1ddf465a-3a81-4419-8272-c4c079ac4fb1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrderOrProductionBacklogMember_9559af99-1414-4e89-9808-64e8130bc839" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OrderOrProductionBacklogMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1ddf465a-3a81-4419-8272-c4c079ac4fb1" xlink:to="loc_us-gaap_OrderOrProductionBacklogMember_9559af99-1414-4e89-9808-64e8130bc839" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_5b9e72e4-430d-4e39-bca0-ba00e8a8ed16" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_84b523fe-a1d4-4c27-a09b-3169908d857e" xlink:to="loc_srt_StatementScenarioAxis_5b9e72e4-430d-4e39-bca0-ba00e8a8ed16" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_5b9e72e4-430d-4e39-bca0-ba00e8a8ed16_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_5b9e72e4-430d-4e39-bca0-ba00e8a8ed16" xlink:to="loc_srt_ScenarioUnspecifiedDomain_5b9e72e4-430d-4e39-bca0-ba00e8a8ed16_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_623e378c-9ee5-41f3-9365-8dcaf737645f" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_5b9e72e4-430d-4e39-bca0-ba00e8a8ed16" xlink:to="loc_srt_ScenarioUnspecifiedDomain_623e378c-9ee5-41f3-9365-8dcaf737645f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScenarioAdjustmentMember_0d3b8ccf-959a-43e3-888d-ca226d6b011f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScenarioAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_623e378c-9ee5-41f3-9365-8dcaf737645f" xlink:to="loc_us-gaap_ScenarioAdjustmentMember_0d3b8ccf-959a-43e3-888d-ca226d6b011f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/AcquisitionsPreliminaryPriceAllocationDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#AcquisitionsPreliminaryPriceAllocationDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/AcquisitionsPreliminaryPriceAllocationDetails" xlink:type="extended" id="ic092dfc91fe6493883803e49f6e8c490_AcquisitionsPreliminaryPriceAllocationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_3a88c064-d7fd-48c4-acbe-13cfd8491588" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_36144fc1-d6d6-4a05-a464-ef894fd0e744" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3a88c064-d7fd-48c4-acbe-13cfd8491588" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_36144fc1-d6d6-4a05-a464-ef894fd0e744" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_0b1567dc-8675-4f46-96ce-cd6a011a7bde" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_36144fc1-d6d6-4a05-a464-ef894fd0e744" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_0b1567dc-8675-4f46-96ce-cd6a011a7bde" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_BusinessCombinationConsiderationTransferredCashSettledStockOptions_010314e6-6773-4a19-9b35-eca581c45edc" xlink:href="lfus-20201226.xsd#lfus_BusinessCombinationConsiderationTransferredCashSettledStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_36144fc1-d6d6-4a05-a464-ef894fd0e744" xlink:to="loc_lfus_BusinessCombinationConsiderationTransferredCashSettledStockOptions_010314e6-6773-4a19-9b35-eca581c45edc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_dcced7c6-997c-42f5-b5b9-45e9383d9f48" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_36144fc1-d6d6-4a05-a464-ef894fd0e744" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_dcced7c6-997c-42f5-b5b9-45e9383d9f48" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_BusinessCombinationConsiderationTransferredConvertedStockOptions_7760cd4b-3613-46dc-8ec7-853fa2f235d2" xlink:href="lfus-20201226.xsd#lfus_BusinessCombinationConsiderationTransferredConvertedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_36144fc1-d6d6-4a05-a464-ef894fd0e744" xlink:to="loc_lfus_BusinessCombinationConsiderationTransferredConvertedStockOptions_7760cd4b-3613-46dc-8ec7-853fa2f235d2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1_7ca3404c-cdcb-4a01-a292-74194fe056ce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_36144fc1-d6d6-4a05-a464-ef894fd0e744" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1_7ca3404c-cdcb-4a01-a292-74194fe056ce" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterestAbstract_0edf4fee-e115-4af7-9b6e-5ec97bad52f5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3a88c064-d7fd-48c4-acbe-13cfd8491588" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterestAbstract_0edf4fee-e115-4af7-9b6e-5ec97bad52f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_f267149a-37df-4fbc-bf8a-ba7ad7e39a20" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterestAbstract_0edf4fee-e115-4af7-9b6e-5ec97bad52f5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_f267149a-37df-4fbc-bf8a-ba7ad7e39a20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_e8738b29-360b-4424-9717-c36eee81161f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterestAbstract_0edf4fee-e115-4af7-9b6e-5ec97bad52f5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_e8738b29-360b-4424-9717-c36eee81161f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_9505af7f-9376-4889-8929-57b037165157" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterestAbstract_0edf4fee-e115-4af7-9b6e-5ec97bad52f5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_9505af7f-9376-4889-8929-57b037165157" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_06380787-7841-4cba-902b-2ee7c4837650" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterestAbstract_0edf4fee-e115-4af7-9b6e-5ec97bad52f5" xlink:to="loc_us-gaap_Goodwill_06380787-7841-4cba-902b-2ee7c4837650" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentAssets_255dfeb9-ce51-4fb4-b7cd-28ffee424eef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterestAbstract_0edf4fee-e115-4af7-9b6e-5ec97bad52f5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentAssets_255dfeb9-ce51-4fb4-b7cd-28ffee424eef" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_63cc9b6a-30b5-44a7-8f16-7a5ab115b76d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterestAbstract_0edf4fee-e115-4af7-9b6e-5ec97bad52f5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_63cc9b6a-30b5-44a7-8f16-7a5ab115b76d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_e1211d07-98d5-4666-8736-21732f51848e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3a88c064-d7fd-48c4-acbe-13cfd8491588" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_e1211d07-98d5-4666-8736-21732f51848e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_32eb0a34-5ebd-4201-86de-451c51a5cc75" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3a88c064-d7fd-48c4-acbe-13cfd8491588" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_32eb0a34-5ebd-4201-86de-451c51a5cc75" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_424a4e3f-6bd3-4190-9c9b-59c4db7ded1e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_32eb0a34-5ebd-4201-86de-451c51a5cc75" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_424a4e3f-6bd3-4190-9c9b-59c4db7ded1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_424a4e3f-6bd3-4190-9c9b-59c4db7ded1e_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_424a4e3f-6bd3-4190-9c9b-59c4db7ded1e" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_424a4e3f-6bd3-4190-9c9b-59c4db7ded1e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_00dd479e-ec35-411f-9985-afdf6e863f43" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_424a4e3f-6bd3-4190-9c9b-59c4db7ded1e" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_00dd479e-ec35-411f-9985-afdf6e863f43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IXYSCorporationMember_4499ea7a-dda9-4269-89f3-f1a4f76e4798" xlink:href="lfus-20201226.xsd#lfus_IXYSCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_00dd479e-ec35-411f-9985-afdf6e863f43" xlink:to="loc_lfus_IXYSCorporationMember_4499ea7a-dda9-4269-89f3-f1a4f76e4798" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/AcquisitionsBusinessAcquisitionProFormaInformationDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#AcquisitionsBusinessAcquisitionProFormaInformationDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/AcquisitionsBusinessAcquisitionProFormaInformationDetails" xlink:type="extended" id="i297c0933a97d4e15ace4c2adff716c72_AcquisitionsBusinessAcquisitionProFormaInformationDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/AcquisitionsProFormaInformationAdjustmentsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#AcquisitionsProFormaInformationAdjustmentsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/AcquisitionsProFormaInformationAdjustmentsDetails" xlink:type="extended" id="i0fe6afbd928649bdab895e459dc10639_AcquisitionsProFormaInformationAdjustmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaInformationNonrecurringAdjustmentLineItems_da5cbaf8-70c0-493e-b4bb-f9a5b285c223" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionProFormaInformationNonrecurringAdjustmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_9f9bc9d1-17cd-4bef-971f-48b630fba42b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionProFormaInformationNonrecurringAdjustmentLineItems_da5cbaf8-70c0-493e-b4bb-f9a5b285c223" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_9f9bc9d1-17cd-4bef-971f-48b630fba42b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaInformationNonrecurringAdjustmentsTable_9293c33d-91a2-45b6-829e-25948ce0b07e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionProFormaInformationNonrecurringAdjustmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionProFormaInformationNonrecurringAdjustmentLineItems_da5cbaf8-70c0-493e-b4bb-f9a5b285c223" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaInformationNonrecurringAdjustmentsTable_9293c33d-91a2-45b6-829e-25948ce0b07e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecurringAdjustmentAxis_97c39d2d-872f-43d2-9539-f8d01c4648ba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NonrecurringAdjustmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_BusinessAcquisitionProFormaInformationNonrecurringAdjustmentsTable_9293c33d-91a2-45b6-829e-25948ce0b07e" xlink:to="loc_us-gaap_NonrecurringAdjustmentAxis_97c39d2d-872f-43d2-9539-f8d01c4648ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecurringAdjustmentDomain_97c39d2d-872f-43d2-9539-f8d01c4648ba_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NonrecurringAdjustmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_NonrecurringAdjustmentAxis_97c39d2d-872f-43d2-9539-f8d01c4648ba" xlink:to="loc_us-gaap_NonrecurringAdjustmentDomain_97c39d2d-872f-43d2-9539-f8d01c4648ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecurringAdjustmentDomain_41a3f117-65da-46b7-9bf4-b259d348754c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NonrecurringAdjustmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_NonrecurringAdjustmentAxis_97c39d2d-872f-43d2-9539-f8d01c4648ba" xlink:to="loc_us-gaap_NonrecurringAdjustmentDomain_41a3f117-65da-46b7-9bf4-b259d348754c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AdjustmentToAmortizationMember_a76e621f-013d-43d2-a520-190a6d4ca42d" xlink:href="lfus-20201226.xsd#lfus_AdjustmentToAmortizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonrecurringAdjustmentDomain_41a3f117-65da-46b7-9bf4-b259d348754c" xlink:to="loc_lfus_AdjustmentToAmortizationMember_a76e621f-013d-43d2-a520-190a6d4ca42d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquisitionRelatedCostsMember_6b5df5d6-6525-4061-b07d-697630fb20e7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AcquisitionRelatedCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonrecurringAdjustmentDomain_41a3f117-65da-46b7-9bf4-b259d348754c" xlink:to="loc_us-gaap_AcquisitionRelatedCostsMember_6b5df5d6-6525-4061-b07d-697630fb20e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AmortizationOfInventoryStepUpMember_17fe1d9b-3c4c-4631-afa4-268c7336f6cf" xlink:href="lfus-20201226.xsd#lfus_AmortizationOfInventoryStepUpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonrecurringAdjustmentDomain_41a3f117-65da-46b7-9bf4-b259d348754c" xlink:to="loc_lfus_AmortizationOfInventoryStepUpMember_17fe1d9b-3c4c-4631-afa4-268c7336f6cf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AdjustmentToStockCompensationMember_768ad054-38f8-4ece-8e86-71bde6e5b2ee" xlink:href="lfus-20201226.xsd#lfus_AdjustmentToStockCompensationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonrecurringAdjustmentDomain_41a3f117-65da-46b7-9bf4-b259d348754c" xlink:to="loc_lfus_AdjustmentToStockCompensationMember_768ad054-38f8-4ece-8e86-71bde6e5b2ee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AdjustmentToIncomeTaxMember_c96e357a-b301-4270-88c2-b7c2f91328d0" xlink:href="lfus-20201226.xsd#lfus_AdjustmentToIncomeTaxMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonrecurringAdjustmentDomain_41a3f117-65da-46b7-9bf4-b259d348754c" xlink:to="loc_lfus_AdjustmentToIncomeTaxMember_c96e357a-b301-4270-88c2-b7c2f91328d0" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/Inventories" xlink:type="simple" xlink:href="lfus-20201226.xsd#Inventories"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/Inventories" xlink:type="extended" id="i8d306a94389742a98ed64fca34476ae5_Inventories"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/InventoriesTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#InventoriesTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/InventoriesTables" xlink:type="extended" id="i47b6c8e7c7614f66b95c6bc2f2666a40_InventoriesTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/InventoriesComponentsofInventoriesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#InventoriesComponentsofInventoriesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/InventoriesComponentsofInventoriesDetails" xlink:type="extended" id="idc124382bb964f03b3589406f8996060_InventoriesComponentsofInventoriesDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/PropertyPlantandEquipment" xlink:type="simple" xlink:href="lfus-20201226.xsd#PropertyPlantandEquipment"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/PropertyPlantandEquipment" xlink:type="extended" id="i288c114c3eb0401790cb6a0d7820a1bc_PropertyPlantandEquipment"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/PropertyPlantandEquipmentTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#PropertyPlantandEquipmentTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/PropertyPlantandEquipmentTables" xlink:type="extended" id="i4ecff0ba0eba4f97837893623023647f_PropertyPlantandEquipmentTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/PropertyPlantandEquipmentDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#PropertyPlantandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/PropertyPlantandEquipmentDetails" xlink:type="extended" id="i97aab3cda3a94a1493ee281d0b605a9c_PropertyPlantandEquipmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8413ab72-8613-4dc0-b337-364d4196b1da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_896eb6bf-cbb4-4045-8c2a-e36af2c59076" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8413ab72-8613-4dc0-b337-364d4196b1da" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_896eb6bf-cbb4-4045-8c2a-e36af2c59076" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_51013aba-aa10-4bc1-b1b3-9fc48ce8d210" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8413ab72-8613-4dc0-b337-364d4196b1da" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_51013aba-aa10-4bc1-b1b3-9fc48ce8d210" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_3e7340c3-1a40-4a7a-9f5c-b966d4577d3a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8413ab72-8613-4dc0-b337-364d4196b1da" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_3e7340c3-1a40-4a7a-9f5c-b966d4577d3a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_ed94c4a9-2423-4be1-a29e-dbcfd220f9c7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8413ab72-8613-4dc0-b337-364d4196b1da" xlink:to="loc_us-gaap_Depreciation_ed94c4a9-2423-4be1-a29e-dbcfd220f9c7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_cdcd3854-06d2-4b9e-964f-51fd4eb968df" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8413ab72-8613-4dc0-b337-364d4196b1da" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_cdcd3854-06d2-4b9e-964f-51fd4eb968df" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_1eb3a672-ee5b-4ccf-99b6-dcfd75d0053c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_cdcd3854-06d2-4b9e-964f-51fd4eb968df" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_1eb3a672-ee5b-4ccf-99b6-dcfd75d0053c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1eb3a672-ee5b-4ccf-99b6-dcfd75d0053c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_1eb3a672-ee5b-4ccf-99b6-dcfd75d0053c" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1eb3a672-ee5b-4ccf-99b6-dcfd75d0053c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e920f8d3-686d-4f41-bc5b-77b3558784fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_1eb3a672-ee5b-4ccf-99b6-dcfd75d0053c" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e920f8d3-686d-4f41-bc5b-77b3558784fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandMember_1b46d975-57cf-4e24-b466-aa8366d2b59a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e920f8d3-686d-4f41-bc5b-77b3558784fc" xlink:to="loc_us-gaap_LandMember_1b46d975-57cf-4e24-b466-aa8366d2b59a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingMember_50cfe765-2384-4239-93fd-f1ca078fd145" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e920f8d3-686d-4f41-bc5b-77b3558784fc" xlink:to="loc_us-gaap_BuildingMember_50cfe765-2384-4239-93fd-f1ca078fd145" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquipmentMember_b5707ea5-3cef-4b85-bd3a-15d22f663f32" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e920f8d3-686d-4f41-bc5b-77b3558784fc" xlink:to="loc_us-gaap_EquipmentMember_b5707ea5-3cef-4b85-bd3a-15d22f663f32" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssets" xlink:type="simple" xlink:href="lfus-20201226.xsd#GoodwillandOtherIntangibleAssets"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssets" xlink:type="extended" id="i339e3d1e6f1b4e5aa0658d96628add80_GoodwillandOtherIntangibleAssets"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssetsTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#GoodwillandOtherIntangibleAssetsTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssetsTables" xlink:type="extended" id="if98bf932d6b14bca966b98ec4093e365_GoodwillandOtherIntangibleAssetsTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssetsAmountsforGoodwillandChangesinCarryingValuebyOperatingSegmentDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#GoodwillandOtherIntangibleAssetsAmountsforGoodwillandChangesinCarryingValuebyOperatingSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssetsAmountsforGoodwillandChangesinCarryingValuebyOperatingSegmentDetails" xlink:type="extended" id="i6458293fc911417c921ac6df812c4c63_GoodwillandOtherIntangibleAssetsAmountsforGoodwillandChangesinCarryingValuebyOperatingSegmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_993c7d77-0c31-4b61-9262-031a8d700101" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_d1425d4d-59d9-44b8-9d76-2072fc4f0f46" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_993c7d77-0c31-4b61-9262-031a8d700101" xlink:to="loc_us-gaap_GoodwillRollForward_d1425d4d-59d9-44b8-9d76-2072fc4f0f46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillGross_c66acfbc-30cf-4611-8792-b3b2686d4a86" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_d1425d4d-59d9-44b8-9d76-2072fc4f0f46" xlink:to="loc_us-gaap_GoodwillGross_c66acfbc-30cf-4611-8792-b3b2686d4a86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLoss_5cdbd749-ff2b-4474-9258-2b4875006c2f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillImpairedAccumulatedImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_d1425d4d-59d9-44b8-9d76-2072fc4f0f46" xlink:to="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLoss_5cdbd749-ff2b-4474-9258-2b4875006c2f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_8a9dc5be-0ccc-4263-9607-c0a1a0d48029" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_d1425d4d-59d9-44b8-9d76-2072fc4f0f46" xlink:to="loc_us-gaap_Goodwill_8a9dc5be-0ccc-4263-9607-c0a1a0d48029" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_67f7481e-9365-4010-85cb-c292244d10fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_d1425d4d-59d9-44b8-9d76-2072fc4f0f46" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_67f7481e-9365-4010-85cb-c292244d10fd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_a5e21cbb-80de-4f1d-8331-14c582bb1777" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_d1425d4d-59d9-44b8-9d76-2072fc4f0f46" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_a5e21cbb-80de-4f1d-8331-14c582bb1777" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_0f496a67-e943-4cb5-87dd-7c33c38f25d6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_993c7d77-0c31-4b61-9262-031a8d700101" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_0f496a67-e943-4cb5-87dd-7c33c38f25d6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_ad3c3eb3-f62e-4c3c-ad31-ce1a4e863370" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_0f496a67-e943-4cb5-87dd-7c33c38f25d6" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_ad3c3eb3-f62e-4c3c-ad31-ce1a4e863370" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_ad3c3eb3-f62e-4c3c-ad31-ce1a4e863370_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_ad3c3eb3-f62e-4c3c-ad31-ce1a4e863370" xlink:to="loc_us-gaap_SegmentDomain_ad3c3eb3-f62e-4c3c-ad31-ce1a4e863370_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_089e530b-608d-4a02-af4a-ceb9f07bda89" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_ad3c3eb3-f62e-4c3c-ad31-ce1a4e863370" xlink:to="loc_us-gaap_SegmentDomain_089e530b-608d-4a02-af4a-ceb9f07bda89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ElectronicsMember_4b848332-05d5-40b3-926d-73c3f80ab543" xlink:href="lfus-20201226.xsd#lfus_ElectronicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_089e530b-608d-4a02-af4a-ceb9f07bda89" xlink:to="loc_lfus_ElectronicsMember_4b848332-05d5-40b3-926d-73c3f80ab543" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AutomotiveMember_eec34cca-283c-4ec5-a45b-37be0d42fe33" xlink:href="lfus-20201226.xsd#lfus_AutomotiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_089e530b-608d-4a02-af4a-ceb9f07bda89" xlink:to="loc_lfus_AutomotiveMember_eec34cca-283c-4ec5-a45b-37be0d42fe33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IndustrialMember_1894d21a-61c0-49d6-91c5-e42679279958" xlink:href="lfus-20201226.xsd#lfus_IndustrialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_089e530b-608d-4a02-af4a-ceb9f07bda89" xlink:to="loc_lfus_IndustrialMember_1894d21a-61c0-49d6-91c5-e42679279958" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#GoodwillandOtherIntangibleAssetsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="extended" id="i6af28e5d0b0f46c78c9768997125599f_GoodwillandOtherIntangibleAssetsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_4d890f2c-98e2-4999-a719-bc79b9699cfb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_07ba723b-bc13-4a4d-b18b-f19c57a736b1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_4d890f2c-98e2-4999-a719-bc79b9699cfb" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_07ba723b-bc13-4a4d-b18b-f19c57a736b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_7b944a70-1874-4c80-8384-a98aa1a87ce7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_4d890f2c-98e2-4999-a719-bc79b9699cfb" xlink:to="loc_us-gaap_Goodwill_7b944a70-1874-4c80-8384-a98aa1a87ce7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_460c3375-605b-492d-b9bb-601279b1917e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinitelivedIntangibleAssetsAcquired1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_4d890f2c-98e2-4999-a719-bc79b9699cfb" xlink:to="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_460c3375-605b-492d-b9bb-601279b1917e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_c7131e60-7e5f-4d62-a01c-5a1af0a76ca2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_4d890f2c-98e2-4999-a719-bc79b9699cfb" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_c7131e60-7e5f-4d62-a01c-5a1af0a76ca2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_5febe646-32c9-4f1c-add5-a8fcf7579a1d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_4d890f2c-98e2-4999-a719-bc79b9699cfb" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_5febe646-32c9-4f1c-add5-a8fcf7579a1d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReportingUnitAxis_4b1c3c12-d3a3-49a9-8bd4-b59db1cd02ff" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReportingUnitAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_5febe646-32c9-4f1c-add5-a8fcf7579a1d" xlink:to="loc_us-gaap_ReportingUnitAxis_4b1c3c12-d3a3-49a9-8bd4-b59db1cd02ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReportingUnitDomain_4b1c3c12-d3a3-49a9-8bd4-b59db1cd02ff_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReportingUnitDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReportingUnitAxis_4b1c3c12-d3a3-49a9-8bd4-b59db1cd02ff" xlink:to="loc_us-gaap_ReportingUnitDomain_4b1c3c12-d3a3-49a9-8bd4-b59db1cd02ff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReportingUnitDomain_14cc59d7-8b5c-4391-b236-b85c2e114665" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReportingUnitDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReportingUnitAxis_4b1c3c12-d3a3-49a9-8bd4-b59db1cd02ff" xlink:to="loc_us-gaap_ReportingUnitDomain_14cc59d7-8b5c-4391-b236-b85c2e114665" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AutomotiveSensorsMember_a2363698-9ffe-477e-8b41-5c0152e368e5" xlink:href="lfus-20201226.xsd#lfus_AutomotiveSensorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReportingUnitDomain_14cc59d7-8b5c-4391-b236-b85c2e114665" xlink:to="loc_lfus_AutomotiveSensorsMember_a2363698-9ffe-477e-8b41-5c0152e368e5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssetsDetailsofOtherIntangibleAssetsandRelatedFutureAmortizationExpenseDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#GoodwillandOtherIntangibleAssetsDetailsofOtherIntangibleAssetsandRelatedFutureAmortizationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssetsDetailsofOtherIntangibleAssetsandRelatedFutureAmortizationExpenseDetails" xlink:type="extended" id="i1efdfb067e2f45f59bcdd5fff23f42c0_GoodwillandOtherIntangibleAssetsDetailsofOtherIntangibleAssetsandRelatedFutureAmortizationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b917d884-dc04-42a6-b7f2-85bef972bfa2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_914cd686-7d0a-47e4-aab1-1fce81ba3b96" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b917d884-dc04-42a6-b7f2-85bef972bfa2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_914cd686-7d0a-47e4-aab1-1fce81ba3b96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_49038f06-44a7-49da-88e2-9838970bc55f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b917d884-dc04-42a6-b7f2-85bef972bfa2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_49038f06-44a7-49da-88e2-9838970bc55f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_abfcdabe-f3c3-4dd1-8fb4-c5e6a65ee14d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b917d884-dc04-42a6-b7f2-85bef972bfa2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_abfcdabe-f3c3-4dd1-8fb4-c5e6a65ee14d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_3c09e752-19fb-477a-8e75-3ff7ff3e56fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b917d884-dc04-42a6-b7f2-85bef972bfa2" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_3c09e752-19fb-477a-8e75-3ff7ff3e56fe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_03d18b6c-16d3-4d59-ab7f-00726ec4320e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinitelivedIntangibleAssetsAcquired1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b917d884-dc04-42a6-b7f2-85bef972bfa2" xlink:to="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_03d18b6c-16d3-4d59-ab7f-00726ec4320e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3e2e86c5-fbc3-4997-a5d9-64c91e69a408" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b917d884-dc04-42a6-b7f2-85bef972bfa2" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3e2e86c5-fbc3-4997-a5d9-64c91e69a408" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_be451875-cced-4eb4-8fa9-a3600fcb9421" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3e2e86c5-fbc3-4997-a5d9-64c91e69a408" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_be451875-cced-4eb4-8fa9-a3600fcb9421" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_be451875-cced-4eb4-8fa9-a3600fcb9421_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_be451875-cced-4eb4-8fa9-a3600fcb9421" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_be451875-cced-4eb4-8fa9-a3600fcb9421_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ad05d32a-4583-4cdb-9c40-1e9e6792460f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_be451875-cced-4eb4-8fa9-a3600fcb9421" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ad05d32a-4583-4cdb-9c40-1e9e6792460f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UseRightsMember_4b8abcd0-8fd2-4806-89c1-8a8eaef02dd3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UseRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ad05d32a-4583-4cdb-9c40-1e9e6792460f" xlink:to="loc_us-gaap_UseRightsMember_4b8abcd0-8fd2-4806-89c1-8a8eaef02dd3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_PatentsLicensesAndSoftwareMember_9acd5ce0-14e4-495c-bb1d-8b80afc2e27b" xlink:href="lfus-20201226.xsd#lfus_PatentsLicensesAndSoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ad05d32a-4583-4cdb-9c40-1e9e6792460f" xlink:to="loc_lfus_PatentsLicensesAndSoftwareMember_9acd5ce0-14e4-495c-bb1d-8b80afc2e27b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DistributionRightsMember_4c5c493e-9c8c-498e-ab41-7bc470be26d8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DistributionRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ad05d32a-4583-4cdb-9c40-1e9e6792460f" xlink:to="loc_us-gaap_DistributionRightsMember_4c5c493e-9c8c-498e-ab41-7bc470be26d8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_CustomerListsTrademarksAndTradeNamesMember_80b4f4b4-6693-472a-ac8d-4263e1579036" xlink:href="lfus-20201226.xsd#lfus_CustomerListsTrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ad05d32a-4583-4cdb-9c40-1e9e6792460f" xlink:to="loc_lfus_CustomerListsTrademarksAndTradeNamesMember_80b4f4b4-6693-472a-ac8d-4263e1579036" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrderOrProductionBacklogMember_017bd418-6a96-4ec8-9038-5a404ead0065" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OrderOrProductionBacklogMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ad05d32a-4583-4cdb-9c40-1e9e6792460f" xlink:to="loc_us-gaap_OrderOrProductionBacklogMember_017bd418-6a96-4ec8-9038-5a404ead0065" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssetsEstimatedAmortizationExpenseRelatedtoIntangibleAssetswithDefiniteLivesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#GoodwillandOtherIntangibleAssetsEstimatedAmortizationExpenseRelatedtoIntangibleAssetswithDefiniteLivesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/GoodwillandOtherIntangibleAssetsEstimatedAmortizationExpenseRelatedtoIntangibleAssetswithDefiniteLivesDetails" xlink:type="extended" id="ieb188e4054a945e7b41d3019f1d49b26_GoodwillandOtherIntangibleAssetsEstimatedAmortizationExpenseRelatedtoIntangibleAssetswithDefiniteLivesDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/AccruedLiabilities" xlink:type="simple" xlink:href="lfus-20201226.xsd#AccruedLiabilities"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/AccruedLiabilities" xlink:type="extended" id="ief46b8453aa3411ca68e8e5ad1e948c8_AccruedLiabilities"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/AccruedLiabilitiesTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#AccruedLiabilitiesTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/AccruedLiabilitiesTables" xlink:type="extended" id="i03874b41fdf847589fd3971fb3dface0_AccruedLiabilitiesTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/AccruedLiabilitiesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#AccruedLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/AccruedLiabilitiesDetails" xlink:type="extended" id="i17aa34beb8a64fb4b613f157dceff862_AccruedLiabilitiesDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/LeaseCommitments" xlink:type="simple" xlink:href="lfus-20201226.xsd#LeaseCommitments"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/LeaseCommitments" xlink:type="extended" id="i668e3233e2364fafaa5aad6a344c44f7_LeaseCommitments"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/LeaseCommitmentsTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#LeaseCommitmentsTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/LeaseCommitmentsTables" xlink:type="extended" id="i1b0e8154d4114026bf804d270179a333_LeaseCommitmentsTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/LeaseCommitmentsBalanceSheetOperatingLeaseTermandDiscountRateDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#LeaseCommitmentsBalanceSheetOperatingLeaseTermandDiscountRateDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/LeaseCommitmentsBalanceSheetOperatingLeaseTermandDiscountRateDetails" xlink:type="extended" id="i8dbad5d9086c440db4ce7d3bfb54e7e2_LeaseCommitmentsBalanceSheetOperatingLeaseTermandDiscountRateDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/LeaseCommitmentsLeaseCostDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#LeaseCommitmentsLeaseCostDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/LeaseCommitmentsLeaseCostDetails" xlink:type="extended" id="i954b023cfc90403c8c6dbe9721868cc1_LeaseCommitmentsLeaseCostDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/LeaseCommitmentsNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#LeaseCommitmentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/LeaseCommitmentsNarrativeDetails" xlink:type="extended" id="ib54845a5e4bc4133ba912d89bea0c3a0_LeaseCommitmentsNarrativeDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/LeaseCommitmentsMaturitiesofLeaseLiabilitiesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#LeaseCommitmentsMaturitiesofLeaseLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/LeaseCommitmentsMaturitiesofLeaseLiabilitiesDetails" xlink:type="extended" id="i728e4b13e6594ce59c81dd4969f09dfc_LeaseCommitmentsMaturitiesofLeaseLiabilitiesDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/LeaseCommitmentsSupplementalCashFlowInformationDetailsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#LeaseCommitmentsSupplementalCashFlowInformationDetailsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/LeaseCommitmentsSupplementalCashFlowInformationDetailsDetails" xlink:type="extended" id="id90965027a1e4adeb98e9cd6602adcd0_LeaseCommitmentsSupplementalCashFlowInformationDetailsDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/RestructuringImpairmentandOtherCharges" xlink:type="simple" xlink:href="lfus-20201226.xsd#RestructuringImpairmentandOtherCharges"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/RestructuringImpairmentandOtherCharges" xlink:type="extended" id="if583c52995ff4d8890d1127c0d1f2e64_RestructuringImpairmentandOtherCharges"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/RestructuringImpairmentandOtherChargesTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#RestructuringImpairmentandOtherChargesTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/RestructuringImpairmentandOtherChargesTables" xlink:type="extended" id="i083db052a84c42858b2d5590af347ab4_RestructuringImpairmentandOtherChargesTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/RestructuringImpairmentandOtherChargesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#RestructuringImpairmentandOtherChargesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/RestructuringImpairmentandOtherChargesDetails" xlink:type="extended" id="id104807319fe4d05942d8dc8f66c5909_RestructuringImpairmentandOtherChargesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_68f93f36-3cb3-47cf-9bf5-c874a3ed7275" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_873b0954-3649-469a-8ff2-de0f454df28f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_68f93f36-3cb3-47cf-9bf5-c874a3ed7275" xlink:to="loc_us-gaap_RestructuringCharges_873b0954-3649-469a-8ff2-de0f454df28f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_d833a34b-9db3-4eab-aa8d-fff4daa562d0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_68f93f36-3cb3-47cf-9bf5-c874a3ed7275" xlink:to="loc_us-gaap_AssetImpairmentCharges_d833a34b-9db3-4eab-aa8d-fff4daa562d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostsAndAssetImpairmentCharges_a6c1d386-ea10-4bca-9ea4-5ca758ef7400" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCostsAndAssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_68f93f36-3cb3-47cf-9bf5-c874a3ed7275" xlink:to="loc_us-gaap_RestructuringCostsAndAssetImpairmentCharges_a6c1d386-ea10-4bca-9ea4-5ca758ef7400" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_ee25ede9-8c19-45e4-b605-6749b9b00c49" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_68f93f36-3cb3-47cf-9bf5-c874a3ed7275" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_ee25ede9-8c19-45e4-b605-6749b9b00c49" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_c8986c20-e3eb-4e1a-8e73-bbdf0ee861a1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_68f93f36-3cb3-47cf-9bf5-c874a3ed7275" xlink:to="loc_us-gaap_RestructuringReserve_c8986c20-e3eb-4e1a-8e73-bbdf0ee861a1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_20d91b2a-25ea-4120-b8b5-c9fbb30f893d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_68f93f36-3cb3-47cf-9bf5-c874a3ed7275" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_20d91b2a-25ea-4120-b8b5-c9fbb30f893d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_c2092b68-a6c2-45d9-ab4d-c053aa4fb776" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_20d91b2a-25ea-4120-b8b5-c9fbb30f893d" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_c2092b68-a6c2-45d9-ab4d-c053aa4fb776" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_c2092b68-a6c2-45d9-ab4d-c053aa4fb776_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_c2092b68-a6c2-45d9-ab4d-c053aa4fb776" xlink:to="loc_us-gaap_SegmentDomain_c2092b68-a6c2-45d9-ab4d-c053aa4fb776_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_9e3441d7-c3ad-4fab-ba7f-4695781f53fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_c2092b68-a6c2-45d9-ab4d-c053aa4fb776" xlink:to="loc_us-gaap_SegmentDomain_9e3441d7-c3ad-4fab-ba7f-4695781f53fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ElectronicsMember_d14e0e47-e868-4227-9412-d7f4ad6691bb" xlink:href="lfus-20201226.xsd#lfus_ElectronicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_9e3441d7-c3ad-4fab-ba7f-4695781f53fd" xlink:to="loc_lfus_ElectronicsMember_d14e0e47-e868-4227-9412-d7f4ad6691bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AutomotiveMember_c0a08f54-9a88-4a8f-82c8-3b8bed0c20e6" xlink:href="lfus-20201226.xsd#lfus_AutomotiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_9e3441d7-c3ad-4fab-ba7f-4695781f53fd" xlink:to="loc_lfus_AutomotiveMember_c0a08f54-9a88-4a8f-82c8-3b8bed0c20e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IndustrialMember_2b6e9c69-04f6-43ac-8e05-89ceb07f893a" xlink:href="lfus-20201226.xsd#lfus_IndustrialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_9e3441d7-c3ad-4fab-ba7f-4695781f53fd" xlink:to="loc_lfus_IndustrialMember_2b6e9c69-04f6-43ac-8e05-89ceb07f893a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_90e0569c-e556-485b-bbef-eebe1a889f95" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_20d91b2a-25ea-4120-b8b5-c9fbb30f893d" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_90e0569c-e556-485b-bbef-eebe1a889f95" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_90e0569c-e556-485b-bbef-eebe1a889f95_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_90e0569c-e556-485b-bbef-eebe1a889f95" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_90e0569c-e556-485b-bbef-eebe1a889f95_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_776056ac-e967-471a-b4d8-aad7056eecf4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_90e0569c-e556-485b-bbef-eebe1a889f95" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_776056ac-e967-471a-b4d8-aad7056eecf4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_4787d8bd-19f4-4341-acf1-a1bee961bb01" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_776056ac-e967-471a-b4d8-aad7056eecf4" xlink:to="loc_us-gaap_EmployeeSeveranceMember_4787d8bd-19f4-4341-acf1-a1bee961bb01" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherRestructuringMember_6054b319-8c94-4317-977e-937beffda750" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherRestructuringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_776056ac-e967-471a-b4d8-aad7056eecf4" xlink:to="loc_us-gaap_OtherRestructuringMember_6054b319-8c94-4317-977e-937beffda750" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/Debt" xlink:type="simple" xlink:href="lfus-20201226.xsd#Debt"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/Debt" xlink:type="extended" id="i0c54ad3f44fd440bbf4ed161b58e14aa_Debt"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/DebtTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#DebtTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/DebtTables" xlink:type="extended" id="i91c6d5325afb457d94c85f18aa006b9e_DebtTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/DebtCarryingAmountsofLongtermDebtDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#DebtCarryingAmountsofLongtermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/DebtCarryingAmountsofLongtermDebtDetails" xlink:type="extended" id="i48c71f4576ba40efb0413c0def9fff4e_DebtCarryingAmountsofLongtermDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_d2f704b2-8e6d-4419-a580-acab4225ae08" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_45f152cf-3f86-4a2d-a5bd-75460453b11c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_d2f704b2-8e6d-4419-a580-acab4225ae08" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_45f152cf-3f86-4a2d-a5bd-75460453b11c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_0e905f2e-f562-4b81-a6d1-7199edfce457" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_d2f704b2-8e6d-4419-a580-acab4225ae08" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_0e905f2e-f562-4b81-a6d1-7199edfce457" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_caff75f8-27d0-4617-9bba-adf0ae6b3f04" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_d2f704b2-8e6d-4419-a580-acab4225ae08" xlink:to="loc_us-gaap_LongTermDebt_caff75f8-27d0-4617-9bba-adf0ae6b3f04" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_e610dd33-caeb-4e80-a98b-966169408419" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_d2f704b2-8e6d-4419-a580-acab4225ae08" xlink:to="loc_us-gaap_LongTermDebtCurrent_e610dd33-caeb-4e80-a98b-966169408419" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_3bb1008f-2fa7-4fda-b2e7-84fbd80bffba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_d2f704b2-8e6d-4419-a580-acab4225ae08" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_3bb1008f-2fa7-4fda-b2e7-84fbd80bffba" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_487ba5e8-a619-425b-a03e-55e8d646f877" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_d2f704b2-8e6d-4419-a580-acab4225ae08" xlink:to="loc_us-gaap_DebtInstrumentTable_487ba5e8-a619-425b-a03e-55e8d646f877" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_14c780cf-a61f-442b-8b72-1e31fa027f24" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_487ba5e8-a619-425b-a03e-55e8d646f877" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_14c780cf-a61f-442b-8b72-1e31fa027f24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_14c780cf-a61f-442b-8b72-1e31fa027f24_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_14c780cf-a61f-442b-8b72-1e31fa027f24" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_14c780cf-a61f-442b-8b72-1e31fa027f24_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_b04be0a2-031e-47da-ae6e-6eb83cdad4d8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_14c780cf-a61f-442b-8b72-1e31fa027f24" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_b04be0a2-031e-47da-ae6e-6eb83cdad4d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_7191d192-b439-4771-8c84-984d1ceccb18" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_b04be0a2-031e-47da-ae6e-6eb83cdad4d8" xlink:to="loc_us-gaap_UnsecuredDebtMember_7191d192-b439-4771-8c84-984d1ceccb18" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_ce134b3f-72c1-4986-85ca-8acaf0c7b867" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_b04be0a2-031e-47da-ae6e-6eb83cdad4d8" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_ce134b3f-72c1-4986-85ca-8acaf0c7b867" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_30898a9d-c1e7-4db8-bd97-7d3a2a59944b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_b04be0a2-031e-47da-ae6e-6eb83cdad4d8" xlink:to="loc_us-gaap_SeniorNotesMember_30898a9d-c1e7-4db8-bd97-7d3a2a59944b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_09cc4761-c35f-4ee2-ac9e-022bb36d72e0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_b04be0a2-031e-47da-ae6e-6eb83cdad4d8" xlink:to="loc_us-gaap_LineOfCreditMember_09cc4761-c35f-4ee2-ac9e-022bb36d72e0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_9bd92164-89dd-447a-9034-8d209682d014" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_487ba5e8-a619-425b-a03e-55e8d646f877" xlink:to="loc_us-gaap_DebtInstrumentAxis_9bd92164-89dd-447a-9034-8d209682d014" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9bd92164-89dd-447a-9034-8d209682d014_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_9bd92164-89dd-447a-9034-8d209682d014" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9bd92164-89dd-447a-9034-8d209682d014_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_94b89286-7eeb-4984-a78a-c48ad84d8a5d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_9bd92164-89dd-447a-9034-8d209682d014" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_94b89286-7eeb-4984-a78a-c48ad84d8a5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_EuroSeniorNotesSeriesAMember_a945eeb8-b99d-40a4-b2e3-8f577b02427e" xlink:href="lfus-20201226.xsd#lfus_EuroSeniorNotesSeriesAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_94b89286-7eeb-4984-a78a-c48ad84d8a5d" xlink:to="loc_lfus_EuroSeniorNotesSeriesAMember_a945eeb8-b99d-40a4-b2e3-8f577b02427e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_EuroSeniorNotesSeriesBMember_9e9fc0d1-33aa-45eb-85b1-a339ffa43337" xlink:href="lfus-20201226.xsd#lfus_EuroSeniorNotesSeriesBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_94b89286-7eeb-4984-a78a-c48ad84d8a5d" xlink:to="loc_lfus_EuroSeniorNotesSeriesBMember_9e9fc0d1-33aa-45eb-85b1-a339ffa43337" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesADue2022Member_d8c46e1a-c115-4772-b635-3b13863116ea" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesADue2022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_94b89286-7eeb-4984-a78a-c48ad84d8a5d" xlink:to="loc_lfus_USSeniorNotesSeriesADue2022Member_d8c46e1a-c115-4772-b635-3b13863116ea" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesBDue2027Member_bc54eacb-3112-40c0-b006-72a5d6b5e7d5" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesBDue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_94b89286-7eeb-4984-a78a-c48ad84d8a5d" xlink:to="loc_lfus_USSeniorNotesSeriesBDue2027Member_bc54eacb-3112-40c0-b006-72a5d6b5e7d5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesADue2025Member_6db66512-f065-4001-a3b8-7f45412ac888" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesADue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_94b89286-7eeb-4984-a78a-c48ad84d8a5d" xlink:to="loc_lfus_USSeniorNotesSeriesADue2025Member_6db66512-f065-4001-a3b8-7f45412ac888" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesBDue2030Member_82e194c2-491f-43d5-acba-aa1a7ded8b14" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesBDue2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_94b89286-7eeb-4984-a78a-c48ad84d8a5d" xlink:to="loc_lfus_USSeniorNotesSeriesBDue2030Member_82e194c2-491f-43d5-acba-aa1a7ded8b14" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/DebtNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#DebtNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/DebtNarrativeDetails" xlink:type="extended" id="i3e0c2a3071ac4b0d9991c616f88230bf_DebtNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_813714aa-6152-4bbd-948e-c10896edc831" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_InterestPaidNet_813714aa-6152-4bbd-948e-c10896edc831" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_e836db60-9104-4a21-8883-2a40085df083" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_DebtInstrumentTerm_e836db60-9104-4a21-8883-2a40085df083" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_DebtAgreementMaximumBorrowingCapacity_218a036f-daea-467b-a04b-1c223273466b" xlink:href="lfus-20201226.xsd#lfus_DebtAgreementMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_lfus_DebtAgreementMaximumBorrowingCapacity_218a036f-daea-467b-a04b-1c223273466b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_a704ab19-2906-4806-8123-f0739bda2a9f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_a704ab19-2906-4806-8123-f0739bda2a9f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_LineofCreditFacilityAdditionalUncommittedBorrowingCapacity_c6af4ebb-796b-44e4-87f8-37caf173f462" xlink:href="lfus-20201226.xsd#lfus_LineofCreditFacilityAdditionalUncommittedBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_lfus_LineofCreditFacilityAdditionalUncommittedBorrowingCapacity_c6af4ebb-796b-44e4-87f8-37caf173f462" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_LineofCreditFacilityAdditionalUncommittedBorrowingCapacityMinimumIncrements_b6029ccf-0dc7-49ae-9c2b-4c40f59b8a07" xlink:href="lfus-20201226.xsd#lfus_LineofCreditFacilityAdditionalUncommittedBorrowingCapacityMinimumIncrements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_lfus_LineofCreditFacilityAdditionalUncommittedBorrowingCapacityMinimumIncrements_b6029ccf-0dc7-49ae-9c2b-4c40f59b8a07" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_NumberofAdvances_5e55df32-89eb-4648-aa3c-7e01757fe45f" xlink:href="lfus-20201226.xsd#lfus_NumberofAdvances"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_lfus_NumberofAdvances_5e55df32-89eb-4648-aa3c-7e01757fe45f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_e9b95fcd-ebc1-4624-b212-542ad525f249" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_e9b95fcd-ebc1-4624-b212-542ad525f249" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_DebtInstrumentQuarterlyPaymentsPercentageofLoan_935d3836-43b3-40cd-9813-a1e2d3c7f104" xlink:href="lfus-20201226.xsd#lfus_DebtInstrumentQuarterlyPaymentsPercentageofLoan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_lfus_DebtInstrumentQuarterlyPaymentsPercentageofLoan_935d3836-43b3-40cd-9813-a1e2d3c7f104" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentPeriodicPayment_8441d597-a83c-455b-9bd1-7c51c7fb5465" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentPeriodicPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_DebtInstrumentPeriodicPayment_8441d597-a83c-455b-9bd1-7c51c7fb5465" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_c85ee980-4637-4e15-bc81-741b134791b9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_c85ee980-4637-4e15-bc81-741b134791b9" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_543bfec6-dfb2-4aba-ba1b-8237a8ded79d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_543bfec6-dfb2-4aba-ba1b-8237a8ded79d" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_LineOfCreditFacilityBorrowingCapacityEliminated_5d5ca614-230f-40ea-9775-ddc8761163f0" xlink:href="lfus-20201226.xsd#lfus_LineOfCreditFacilityBorrowingCapacityEliminated"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_lfus_LineOfCreditFacilityBorrowingCapacityEliminated_5d5ca614-230f-40ea-9775-ddc8761163f0" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_a9142dcc-4799-4ed7-98f2-5b7de87298d1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_a9142dcc-4799-4ed7-98f2-5b7de87298d1" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_f728fde9-98ad-4619-b94c-c291498ec9ed" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_f728fde9-98ad-4619-b94c-c291498ec9ed" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_16845c4f-3ccc-4b88-9316-f18b19e04d83" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_16845c4f-3ccc-4b88-9316-f18b19e04d83" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_2eebdd1a-e84e-4924-860a-faeb26005344" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_2eebdd1a-e84e-4924-860a-faeb26005344" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_de642c3e-57cd-440c-af7d-194c8e803dbc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_de642c3e-57cd-440c-af7d-194c8e803dbc" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_636c34a4-c089-4acc-8a7f-730f6e2ac528" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_636c34a4-c089-4acc-8a7f-730f6e2ac528" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_1d178b67-7882-4a91-a602-5576ebe32ee8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_1d178b67-7882-4a91-a602-5576ebe32ee8" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_9925e7e8-15f5-4e30-b837-eb476113a42b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_9925e7e8-15f5-4e30-b837-eb476113a42b" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_NumberofSeries_b59c1c06-325c-49da-910f-2e18df762f9c" xlink:href="lfus-20201226.xsd#lfus_NumberofSeries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_lfus_NumberofSeries_b59c1c06-325c-49da-910f-2e18df762f9c" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_0bc1ca76-b30e-47c5-be73-90c8a8ac709e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_0bc1ca76-b30e-47c5-be73-90c8a8ac709e" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_b2ab9d98-d019-4824-9264-4230516717d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_b2ab9d98-d019-4824-9264-4230516717d7" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_20f96d44-e9f1-4cb2-ad57-3d45d86896df" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_20f96d44-e9f1-4cb2-ad57-3d45d86896df" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_fc283478-e1ae-47cc-8d58-479f8b2d6cda" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ac189c1-5176-4d1f-a4a0-962447178f56" xlink:to="loc_us-gaap_DebtInstrumentTable_fc283478-e1ae-47cc-8d58-479f8b2d6cda" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_4eba6203-c344-44fd-92f9-981c0260dbb5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_fc283478-e1ae-47cc-8d58-479f8b2d6cda" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_4eba6203-c344-44fd-92f9-981c0260dbb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4eba6203-c344-44fd-92f9-981c0260dbb5_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4eba6203-c344-44fd-92f9-981c0260dbb5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4eba6203-c344-44fd-92f9-981c0260dbb5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ae7999fa-d118-40fb-b225-8262650dacec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4eba6203-c344-44fd-92f9-981c0260dbb5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ae7999fa-d118-40fb-b225-8262650dacec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_5db3da27-7923-4fdc-8e9c-2f8f659ee61e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_ae7999fa-d118-40fb-b225-8262650dacec" xlink:to="loc_us-gaap_SeniorNotesMember_5db3da27-7923-4fdc-8e9c-2f8f659ee61e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_ec492873-2866-4142-8cca-293ebebf017f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_ae7999fa-d118-40fb-b225-8262650dacec" xlink:to="loc_us-gaap_UnsecuredDebtMember_ec492873-2866-4142-8cca-293ebebf017f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_e5a811cd-3631-490a-9c27-183d4da7b27c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_ae7999fa-d118-40fb-b225-8262650dacec" xlink:to="loc_us-gaap_LineOfCreditMember_e5a811cd-3631-490a-9c27-183d4da7b27c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_ec3baea4-73fa-416a-a8f4-a9ad5fd093a4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_fc283478-e1ae-47cc-8d58-479f8b2d6cda" xlink:to="loc_us-gaap_DebtInstrumentAxis_ec3baea4-73fa-416a-a8f4-a9ad5fd093a4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ec3baea4-73fa-416a-a8f4-a9ad5fd093a4_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_ec3baea4-73fa-416a-a8f4-a9ad5fd093a4" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ec3baea4-73fa-416a-a8f4-a9ad5fd093a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_ec3baea4-73fa-416a-a8f4-a9ad5fd093a4" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_CreditAgreementMember_3d2ff73b-1702-46f4-901e-46fa2edfd9e7" xlink:href="lfus-20201226.xsd#lfus_CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:to="loc_lfus_CreditAgreementMember_3d2ff73b-1702-46f4-901e-46fa2edfd9e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_EuroSeniorNotesSeriesAAndBMember_fc72f69f-befb-4c0e-b67a-bb6ebe5c1687" xlink:href="lfus-20201226.xsd#lfus_EuroSeniorNotesSeriesAAndBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:to="loc_lfus_EuroSeniorNotesSeriesAAndBMember_fc72f69f-befb-4c0e-b67a-bb6ebe5c1687" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_EuroSeniorNotesSeriesAMember_b055db0c-f5d2-4320-9e41-1951fd7cfd7e" xlink:href="lfus-20201226.xsd#lfus_EuroSeniorNotesSeriesAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:to="loc_lfus_EuroSeniorNotesSeriesAMember_b055db0c-f5d2-4320-9e41-1951fd7cfd7e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_EuroSeniorNotesSeriesBMember_d67c479f-06e5-473d-961d-f83632314532" xlink:href="lfus-20201226.xsd#lfus_EuroSeniorNotesSeriesBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:to="loc_lfus_EuroSeniorNotesSeriesBMember_d67c479f-06e5-473d-961d-f83632314532" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesAAndBMember_ebb2222b-653c-465f-bbac-626bb39c1d9e" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesAAndBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:to="loc_lfus_USSeniorNotesSeriesAAndBMember_ebb2222b-653c-465f-bbac-626bb39c1d9e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesADue2022Member_471d65bd-2a01-4138-bde9-bb91caa767da" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesADue2022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:to="loc_lfus_USSeniorNotesSeriesADue2022Member_471d65bd-2a01-4138-bde9-bb91caa767da" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesBDue2027Member_be5418b4-3ceb-4562-ae63-e0e71b4e1eda" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesBDue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:to="loc_lfus_USSeniorNotesSeriesBDue2027Member_be5418b4-3ceb-4562-ae63-e0e71b4e1eda" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesAAndBDue2025And2030Member_545e8f62-8713-4ff2-a369-18e8f9fe4ce4" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesAAndBDue2025And2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:to="loc_lfus_USSeniorNotesAAndBDue2025And2030Member_545e8f62-8713-4ff2-a369-18e8f9fe4ce4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesADue2025Member_326d74c8-e526-4ab6-b142-c7dc3f273615" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesADue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:to="loc_lfus_USSeniorNotesSeriesADue2025Member_326d74c8-e526-4ab6-b142-c7dc3f273615" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesBDue2030Member_c1b32e0b-18e9-487b-afa9-82383252ce33" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesBDue2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8a70a52d-3a40-4722-802c-9d4213123d1d" xlink:to="loc_lfus_USSeniorNotesSeriesBDue2030Member_c1b32e0b-18e9-487b-afa9-82383252ce33" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_97f61445-a44b-4ca9-a702-114c1b7b7eba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_fc283478-e1ae-47cc-8d58-479f8b2d6cda" xlink:to="loc_us-gaap_CreditFacilityAxis_97f61445-a44b-4ca9-a702-114c1b7b7eba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_97f61445-a44b-4ca9-a702-114c1b7b7eba_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_97f61445-a44b-4ca9-a702-114c1b7b7eba" xlink:to="loc_us-gaap_CreditFacilityDomain_97f61445-a44b-4ca9-a702-114c1b7b7eba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_4e6ecb1f-8a89-4e12-ac49-3a2016a27213" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_97f61445-a44b-4ca9-a702-114c1b7b7eba" xlink:to="loc_us-gaap_CreditFacilityDomain_4e6ecb1f-8a89-4e12-ac49-3a2016a27213" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_189bab4d-e34f-4b90-837c-5ab3ae6c7796" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_4e6ecb1f-8a89-4e12-ac49-3a2016a27213" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_189bab4d-e34f-4b90-837c-5ab3ae6c7796" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_TermLoanCreditFacilityMember_5ba16956-68c3-4068-85ef-88a06ed1b505" xlink:href="lfus-20201226.xsd#lfus_TermLoanCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_4e6ecb1f-8a89-4e12-ac49-3a2016a27213" xlink:to="loc_lfus_TermLoanCreditFacilityMember_5ba16956-68c3-4068-85ef-88a06ed1b505" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_30000b03-ae25-4217-966f-3a87ecb946fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_fc283478-e1ae-47cc-8d58-479f8b2d6cda" xlink:to="loc_us-gaap_VariableRateAxis_30000b03-ae25-4217-966f-3a87ecb946fd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_30000b03-ae25-4217-966f-3a87ecb946fd_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_30000b03-ae25-4217-966f-3a87ecb946fd" xlink:to="loc_us-gaap_VariableRateDomain_30000b03-ae25-4217-966f-3a87ecb946fd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_a4f7199c-c339-4d28-853a-2f69ecf5c7f1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_30000b03-ae25-4217-966f-3a87ecb946fd" xlink:to="loc_us-gaap_VariableRateDomain_a4f7199c-c339-4d28-853a-2f69ecf5c7f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_6dd29d33-2cf0-4932-af5e-aca78e68c84a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_a4f7199c-c339-4d28-853a-2f69ecf5c7f1" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_6dd29d33-2cf0-4932-af5e-aca78e68c84a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BaseRateMember_fc21de46-8ebb-429a-aa86-77d7790d68cb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BaseRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_a4f7199c-c339-4d28-853a-2f69ecf5c7f1" xlink:to="loc_us-gaap_BaseRateMember_fc21de46-8ebb-429a-aa86-77d7790d68cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_85c98123-fdad-4169-87e2-b39ac0992d3c" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_fc283478-e1ae-47cc-8d58-479f8b2d6cda" xlink:to="loc_srt_RangeAxis_85c98123-fdad-4169-87e2-b39ac0992d3c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_85c98123-fdad-4169-87e2-b39ac0992d3c_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_85c98123-fdad-4169-87e2-b39ac0992d3c" xlink:to="loc_srt_RangeMember_85c98123-fdad-4169-87e2-b39ac0992d3c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_82c2410b-87f4-447f-ac40-18e437aa2089" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_85c98123-fdad-4169-87e2-b39ac0992d3c" xlink:to="loc_srt_RangeMember_82c2410b-87f4-447f-ac40-18e437aa2089" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_ba75806c-1564-46ec-bb97-15a0e6ff5a54" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_82c2410b-87f4-447f-ac40-18e437aa2089" xlink:to="loc_srt_MinimumMember_ba75806c-1564-46ec-bb97-15a0e6ff5a54" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_0630c100-31ea-4747-8c5f-13d4906176d0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_82c2410b-87f4-447f-ac40-18e437aa2089" xlink:to="loc_srt_MaximumMember_0630c100-31ea-4747-8c5f-13d4906176d0" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/DebtScheduledMaturitiesoftheCompanysLongTermDebtDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#DebtScheduledMaturitiesoftheCompanysLongTermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/DebtScheduledMaturitiesoftheCompanysLongTermDebtDetails" xlink:type="extended" id="id812408641a94bfe81cf8f6163f8af8e_DebtScheduledMaturitiesoftheCompanysLongTermDebtDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/FairValueofAssetsandLiabilities" xlink:type="simple" xlink:href="lfus-20201226.xsd#FairValueofAssetsandLiabilities"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/FairValueofAssetsandLiabilities" xlink:type="extended" id="id63dac4904a54fc7a3facdb0cf5ad6b5_FairValueofAssetsandLiabilities"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/FairValueofAssetsandLiabilitiesTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#FairValueofAssetsandLiabilitiesTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/FairValueofAssetsandLiabilitiesTables" xlink:type="extended" id="i2a2d78cdd263417caae2e26e704bd269_FairValueofAssetsandLiabilitiesTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/FairValueofAssetsandLiabilitiesNarrativesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#FairValueofAssetsandLiabilitiesNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/FairValueofAssetsandLiabilitiesNarrativesDetails" xlink:type="extended" id="i518d1f6af04149e786ed4e645d939abd_FairValueofAssetsandLiabilitiesNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_70490dcc-02fa-4872-85b6-e66ee4ded54d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_65458815-f199-4c3c-94fc-6f21c42e45db" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_70490dcc-02fa-4872-85b6-e66ee4ded54d" xlink:to="loc_us-gaap_AssetImpairmentCharges_65458815-f199-4c3c-94fc-6f21c42e45db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNi_04939830-1b90-4ef3-8bb3-c97b85efb694" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_70490dcc-02fa-4872-85b6-e66ee4ded54d" xlink:to="loc_us-gaap_EquitySecuritiesFvNi_04939830-1b90-4ef3-8bb3-c97b85efb694" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_8cd330bc-eee5-428e-98a3-74bd37ea61df" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_70490dcc-02fa-4872-85b6-e66ee4ded54d" xlink:to="loc_us-gaap_DerivativeNotionalAmount_8cd330bc-eee5-428e-98a3-74bd37ea61df" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfDerivatives_092d98d7-4a46-4212-9a6f-8b2ae11ee8bf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainLossOnSaleOfDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_70490dcc-02fa-4872-85b6-e66ee4ded54d" xlink:to="loc_us-gaap_GainLossOnSaleOfDerivatives_092d98d7-4a46-4212-9a6f-8b2ae11ee8bf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetImpairmentCharges_ff218ba2-46b0-471d-91c3-13bacddaf309" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_70490dcc-02fa-4872-85b6-e66ee4ded54d" xlink:to="loc_us-gaap_OtherAssetImpairmentCharges_ff218ba2-46b0-471d-91c3-13bacddaf309" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_a37c8acb-55c3-4852-ac50-5bc18cce67ce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_70490dcc-02fa-4872-85b6-e66ee4ded54d" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_a37c8acb-55c3-4852-ac50-5bc18cce67ce" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_8efcae8c-fdf5-47fd-825b-d02d907a6c78" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_a37c8acb-55c3-4852-ac50-5bc18cce67ce" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_8efcae8c-fdf5-47fd-825b-d02d907a6c78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_8efcae8c-fdf5-47fd-825b-d02d907a6c78_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_8efcae8c-fdf5-47fd-825b-d02d907a6c78" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_8efcae8c-fdf5-47fd-825b-d02d907a6c78_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_04463dc5-c046-4b3c-ab44-7e167cb71f0c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_8efcae8c-fdf5-47fd-825b-d02d907a6c78" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_04463dc5-c046-4b3c-ab44-7e167cb71f0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_aed05dca-561b-4960-8976-e2f3336f7574" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_04463dc5-c046-4b3c-ab44-7e167cb71f0c" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_aed05dca-561b-4960-8976-e2f3336f7574" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_da433406-304f-4a55-a5ea-bfdfd7e06350" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_a37c8acb-55c3-4852-ac50-5bc18cce67ce" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_da433406-304f-4a55-a5ea-bfdfd7e06350" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_da433406-304f-4a55-a5ea-bfdfd7e06350_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_da433406-304f-4a55-a5ea-bfdfd7e06350" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_da433406-304f-4a55-a5ea-bfdfd7e06350_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_95948587-9b1b-4248-b96b-fc3de55919dd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_da433406-304f-4a55-a5ea-bfdfd7e06350" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_95948587-9b1b-4248-b96b-fc3de55919dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_72791ffa-8f13-4258-a749-c5703fef5a32" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_95948587-9b1b-4248-b96b-fc3de55919dd" xlink:to="loc_us-gaap_PatentsMember_72791ffa-8f13-4258-a749-c5703fef5a32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_fcb43326-45cc-489b-9cac-4ffba4447d71" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_a37c8acb-55c3-4852-ac50-5bc18cce67ce" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_fcb43326-45cc-489b-9cac-4ffba4447d71" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_fcb43326-45cc-489b-9cac-4ffba4447d71_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_fcb43326-45cc-489b-9cac-4ffba4447d71" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_fcb43326-45cc-489b-9cac-4ffba4447d71_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_be7f6880-f661-432a-9126-91797d13903c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_fcb43326-45cc-489b-9cac-4ffba4447d71" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_be7f6880-f661-432a-9126-91797d13903c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_OtherExpenseIncomeMember_12d25f5b-b8ac-4848-a5af-9293c8d8dcce" xlink:href="lfus-20201226.xsd#lfus_OtherExpenseIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_be7f6880-f661-432a-9126-91797d13903c" xlink:to="loc_lfus_OtherExpenseIncomeMember_12d25f5b-b8ac-4848-a5af-9293c8d8dcce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_d0f3e9dd-c175-4c95-a237-d80f19f4205f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_a37c8acb-55c3-4852-ac50-5bc18cce67ce" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_d0f3e9dd-c175-4c95-a237-d80f19f4205f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_d0f3e9dd-c175-4c95-a237-d80f19f4205f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_d0f3e9dd-c175-4c95-a237-d80f19f4205f" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_d0f3e9dd-c175-4c95-a237-d80f19f4205f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_ee9186ae-3623-43fd-925b-9e1881596c99" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_d0f3e9dd-c175-4c95-a237-d80f19f4205f" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_ee9186ae-3623-43fd-925b-9e1881596c99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMember_9a435d89-be8e-4579-9506-cc9ab73c4b65" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_ee9186ae-3623-43fd-925b-9e1881596c99" xlink:to="loc_us-gaap_OtherAssetsMember_9a435d89-be8e-4579-9506-cc9ab73c4b65" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/FairValueofAssetsandLiabilitiesAssetsMeasuredatFairValueDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#FairValueofAssetsandLiabilitiesAssetsMeasuredatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/FairValueofAssetsandLiabilitiesAssetsMeasuredatFairValueDetails" xlink:type="extended" id="i829fe3af1d604153a08a5ef4370d5cff_FairValueofAssetsandLiabilitiesAssetsMeasuredatFairValueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c81b6d4f-fdc0-454f-acf2-f7f472619cee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_ab659f55-4e48-48f4-b0c6-f8d8e50ce9ac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c81b6d4f-fdc0-454f-acf2-f7f472619cee" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_ab659f55-4e48-48f4-b0c6-f8d8e50ce9ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNi_47d2365b-f32b-4077-927d-6ba933a1e560" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c81b6d4f-fdc0-454f-acf2-f7f472619cee" xlink:to="loc_us-gaap_EquitySecuritiesFvNi_47d2365b-f32b-4077-927d-6ba933a1e560" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingSecuritiesDebt_9e0d3f0f-2d25-4c0a-8b9a-64f5d58bbf16" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TradingSecuritiesDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c81b6d4f-fdc0-454f-acf2-f7f472619cee" xlink:to="loc_us-gaap_TradingSecuritiesDebt_9e0d3f0f-2d25-4c0a-8b9a-64f5d58bbf16" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_37c5727e-af12-4c4f-8c39-304a2e2bb2ca" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c81b6d4f-fdc0-454f-acf2-f7f472619cee" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_37c5727e-af12-4c4f-8c39-304a2e2bb2ca" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1a4ccdd6-f3d8-474e-b49b-5503f98012b7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c81b6d4f-fdc0-454f-acf2-f7f472619cee" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1a4ccdd6-f3d8-474e-b49b-5503f98012b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8957c791-faf5-48b8-984e-97433b8ae599" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1a4ccdd6-f3d8-474e-b49b-5503f98012b7" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8957c791-faf5-48b8-984e-97433b8ae599" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8957c791-faf5-48b8-984e-97433b8ae599_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8957c791-faf5-48b8-984e-97433b8ae599" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8957c791-faf5-48b8-984e-97433b8ae599_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_13e97b99-1393-4892-a644-6eaf23e94dfe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8957c791-faf5-48b8-984e-97433b8ae599" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_13e97b99-1393-4892-a644-6eaf23e94dfe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_ca1b8ba9-7930-4a30-b342-6bbe3933c110" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_13e97b99-1393-4892-a644-6eaf23e94dfe" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_ca1b8ba9-7930-4a30-b342-6bbe3933c110" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_cb3db414-9302-4fd2-a2c2-8e0dce2408f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_13e97b99-1393-4892-a644-6eaf23e94dfe" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_cb3db414-9302-4fd2-a2c2-8e0dce2408f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_93b05b8e-94f4-4d34-8f68-8659ffde34f3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_13e97b99-1393-4892-a644-6eaf23e94dfe" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_93b05b8e-94f4-4d34-8f68-8659ffde34f3" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/FairValueofAssetsandLiabilitiesCarryingValueandEstimatedFairValueofSeniorNotesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#FairValueofAssetsandLiabilitiesCarryingValueandEstimatedFairValueofSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/FairValueofAssetsandLiabilitiesCarryingValueandEstimatedFairValueofSeniorNotesDetails" xlink:type="extended" id="i8214fc26b5c84a099886f87a2b056593_FairValueofAssetsandLiabilitiesCarryingValueandEstimatedFairValueofSeniorNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_5ecc082d-a6ab-40e5-bc46-f9191961438c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_56739559-62ca-4678-8c9f-06014e6c88a5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_5ecc082d-a6ab-40e5-bc46-f9191961438c" xlink:to="loc_us-gaap_LongTermDebtFairValue_56739559-62ca-4678-8c9f-06014e6c88a5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_9e071de9-482a-4c04-aec9-b8071cc5f31e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_5ecc082d-a6ab-40e5-bc46-f9191961438c" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_9e071de9-482a-4c04-aec9-b8071cc5f31e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_dcb50a7f-1ff8-4dd2-ab99-92d42693b1fb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_9e071de9-482a-4c04-aec9-b8071cc5f31e" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_dcb50a7f-1ff8-4dd2-ab99-92d42693b1fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_dcb50a7f-1ff8-4dd2-ab99-92d42693b1fb_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_dcb50a7f-1ff8-4dd2-ab99-92d42693b1fb" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_dcb50a7f-1ff8-4dd2-ab99-92d42693b1fb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_45bd7ec3-f42b-4d16-a3c3-0c0b795ec72f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_dcb50a7f-1ff8-4dd2-ab99-92d42693b1fb" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_45bd7ec3-f42b-4d16-a3c3-0c0b795ec72f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_988aef62-e0ce-44df-aebc-9f9e5f07a0d4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_45bd7ec3-f42b-4d16-a3c3-0c0b795ec72f" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_988aef62-e0ce-44df-aebc-9f9e5f07a0d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_83177210-cbb2-4008-ab52-bffc35a3fe85" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_988aef62-e0ce-44df-aebc-9f9e5f07a0d4" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_83177210-cbb2-4008-ab52-bffc35a3fe85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_224c45a0-15a5-4a23-9850-ed2b3cd28589" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_988aef62-e0ce-44df-aebc-9f9e5f07a0d4" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_224c45a0-15a5-4a23-9850-ed2b3cd28589" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_9e543f34-7ab2-4a01-a1a6-4c60580a51eb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_9e071de9-482a-4c04-aec9-b8071cc5f31e" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_9e543f34-7ab2-4a01-a1a6-4c60580a51eb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_9e543f34-7ab2-4a01-a1a6-4c60580a51eb_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_9e543f34-7ab2-4a01-a1a6-4c60580a51eb" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_9e543f34-7ab2-4a01-a1a6-4c60580a51eb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_fb634d12-a5b9-4aee-a079-f88a8b382d26" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_9e543f34-7ab2-4a01-a1a6-4c60580a51eb" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_fb634d12-a5b9-4aee-a079-f88a8b382d26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_8a2781a5-b96e-4a96-9870-030024f13512" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_fb634d12-a5b9-4aee-a079-f88a8b382d26" xlink:to="loc_us-gaap_SeniorNotesMember_8a2781a5-b96e-4a96-9870-030024f13512" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_964a7312-9abc-43db-a163-d3b7930e2d20" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_9e071de9-482a-4c04-aec9-b8071cc5f31e" xlink:to="loc_us-gaap_DebtInstrumentAxis_964a7312-9abc-43db-a163-d3b7930e2d20" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_964a7312-9abc-43db-a163-d3b7930e2d20_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_964a7312-9abc-43db-a163-d3b7930e2d20" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_964a7312-9abc-43db-a163-d3b7930e2d20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_fcad26f6-ff57-47e3-ad4a-94aab7266d69" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_964a7312-9abc-43db-a163-d3b7930e2d20" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_fcad26f6-ff57-47e3-ad4a-94aab7266d69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_EuroSeniorNotesSeriesAMember_e3f1015a-8939-45e3-ae3d-9b00a7bb6fc1" xlink:href="lfus-20201226.xsd#lfus_EuroSeniorNotesSeriesAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fcad26f6-ff57-47e3-ad4a-94aab7266d69" xlink:to="loc_lfus_EuroSeniorNotesSeriesAMember_e3f1015a-8939-45e3-ae3d-9b00a7bb6fc1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_EuroSeniorNotesSeriesBMember_ac9c12bd-1ec9-45c8-a55e-28073ced429d" xlink:href="lfus-20201226.xsd#lfus_EuroSeniorNotesSeriesBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fcad26f6-ff57-47e3-ad4a-94aab7266d69" xlink:to="loc_lfus_EuroSeniorNotesSeriesBMember_ac9c12bd-1ec9-45c8-a55e-28073ced429d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesADue2022Member_587927c8-ffdf-4700-8fd0-4bdae980e9b4" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesADue2022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fcad26f6-ff57-47e3-ad4a-94aab7266d69" xlink:to="loc_lfus_USSeniorNotesSeriesADue2022Member_587927c8-ffdf-4700-8fd0-4bdae980e9b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesBDue2027Member_9a1ee18a-805c-408b-b0e7-a682bf8199f7" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesBDue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fcad26f6-ff57-47e3-ad4a-94aab7266d69" xlink:to="loc_lfus_USSeniorNotesSeriesBDue2027Member_9a1ee18a-805c-408b-b0e7-a682bf8199f7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesADue2025Member_066b78d5-6cf9-4e20-aa72-d7863710259f" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesADue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fcad26f6-ff57-47e3-ad4a-94aab7266d69" xlink:to="loc_lfus_USSeniorNotesSeriesADue2025Member_066b78d5-6cf9-4e20-aa72-d7863710259f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_USSeniorNotesSeriesBDue2030Member_d81b7847-74b7-416b-8960-e9322fa66b16" xlink:href="lfus-20201226.xsd#lfus_USSeniorNotesSeriesBDue2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fcad26f6-ff57-47e3-ad4a-94aab7266d69" xlink:to="loc_lfus_USSeniorNotesSeriesBDue2030Member_d81b7847-74b7-416b-8960-e9322fa66b16" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/FairValueofAssetsandLiabilitiesDetailsofimpairmentoflonglivedassetsheldandusedbyassetDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#FairValueofAssetsandLiabilitiesDetailsofimpairmentoflonglivedassetsheldandusedbyassetDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/FairValueofAssetsandLiabilitiesDetailsofimpairmentoflonglivedassetsheldandusedbyassetDetails" xlink:type="extended" id="i8d98f07d334a46898607bc9a01bb5141_FairValueofAssetsandLiabilitiesDetailsofimpairmentoflonglivedassetsheldandusedbyassetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_9115f7f4-647a-4075-88f3-51c8c1cdb683" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetImpairment_5668f138-7bca-4f80-a410-2b09e729e029" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_9115f7f4-647a-4075-88f3-51c8c1cdb683" xlink:to="loc_us-gaap_GoodwillAndIntangibleAssetImpairment_5668f138-7bca-4f80-a410-2b09e729e029" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_b1fb7891-8a15-4d09-b697-2628329367dc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_9115f7f4-647a-4075-88f3-51c8c1cdb683" xlink:to="loc_us-gaap_Goodwill_b1fb7891-8a15-4d09-b697-2628329367dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_908b18da-3c3b-4021-8752-f292e9ffa7e5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_9115f7f4-647a-4075-88f3-51c8c1cdb683" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_908b18da-3c3b-4021-8752-f292e9ffa7e5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_82441f82-55e1-48f3-9073-63b9e9f0e52e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_908b18da-3c3b-4021-8752-f292e9ffa7e5" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_82441f82-55e1-48f3-9073-63b9e9f0e52e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_82441f82-55e1-48f3-9073-63b9e9f0e52e_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_82441f82-55e1-48f3-9073-63b9e9f0e52e" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_82441f82-55e1-48f3-9073-63b9e9f0e52e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_baa5836e-d786-424e-87b6-3931d81fc749" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_82441f82-55e1-48f3-9073-63b9e9f0e52e" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_baa5836e-d786-424e-87b6-3931d81fc749" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsNonrecurringMember_323d0411-58e2-46d6-a348-d61f1602fab5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsNonrecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_baa5836e-d786-424e-87b6-3931d81fc749" xlink:to="loc_us-gaap_FairValueMeasurementsNonrecurringMember_323d0411-58e2-46d6-a348-d61f1602fab5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_e6f8a0a4-26fe-45e6-b36b-67f376112f83" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_908b18da-3c3b-4021-8752-f292e9ffa7e5" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_e6f8a0a4-26fe-45e6-b36b-67f376112f83" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_e6f8a0a4-26fe-45e6-b36b-67f376112f83_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_e6f8a0a4-26fe-45e6-b36b-67f376112f83" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_e6f8a0a4-26fe-45e6-b36b-67f376112f83_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_f0300f8c-2ad7-45f4-8cd8-09480f40c501" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_e6f8a0a4-26fe-45e6-b36b-67f376112f83" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_f0300f8c-2ad7-45f4-8cd8-09480f40c501" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_c43b1d10-0b23-4dab-b6b9-be2af6ea1923" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_f0300f8c-2ad7-45f4-8cd8-09480f40c501" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_c43b1d10-0b23-4dab-b6b9-be2af6ea1923" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_253441e5-2c68-4857-acf5-c2d17e68775e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_c43b1d10-0b23-4dab-b6b9-be2af6ea1923" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_253441e5-2c68-4857-acf5-c2d17e68775e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_081a4e0f-49cb-475f-883a-c9f814345223" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_c43b1d10-0b23-4dab-b6b9-be2af6ea1923" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_081a4e0f-49cb-475f-883a-c9f814345223" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b1d53ab7-71f3-4539-a3a1-1a7402e4988e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_908b18da-3c3b-4021-8752-f292e9ffa7e5" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b1d53ab7-71f3-4539-a3a1-1a7402e4988e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b1d53ab7-71f3-4539-a3a1-1a7402e4988e_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b1d53ab7-71f3-4539-a3a1-1a7402e4988e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b1d53ab7-71f3-4539-a3a1-1a7402e4988e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_202490d3-d5f1-41f7-a34a-155958d1374b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b1d53ab7-71f3-4539-a3a1-1a7402e4988e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_202490d3-d5f1-41f7-a34a-155958d1374b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_bec78b61-8ffb-40b6-877a-771ff7d1f338" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_202490d3-d5f1-41f7-a34a-155958d1374b" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_bec78b61-8ffb-40b6-877a-771ff7d1f338" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlans" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlans"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlans" xlink:type="extended" id="idd1b11e6a5224890bebc778260292b94_BenefitPlans"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansTables" xlink:type="extended" id="id4a2ffc6b78049da8bbb0eefdeadc36a_BenefitPlansTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansNarrativeDetails" xlink:type="extended" id="ia5ad8ac590ae49eaa145645ee905a755_BenefitPlansNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_DefinedBenefitPlanEstimatedReductionInPensionBenefitObligationFromGroupAnnuityContract_d39db3de-162d-436f-8e80-27175c50aeeb" xlink:href="lfus-20201226.xsd#lfus_DefinedBenefitPlanEstimatedReductionInPensionBenefitObligationFromGroupAnnuityContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_lfus_DefinedBenefitPlanEstimatedReductionInPensionBenefitObligationFromGroupAnnuityContract_d39db3de-162d-436f-8e80-27175c50aeeb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_DefinedBenefitPlanEstimatedReductionInPensionBenefitObligationFromGroupAnnuityContractPercent_5a20339f-25c4-4c0e-a09d-314acac148d0" xlink:href="lfus-20201226.xsd#lfus_DefinedBenefitPlanEstimatedReductionInPensionBenefitObligationFromGroupAnnuityContractPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_lfus_DefinedBenefitPlanEstimatedReductionInPensionBenefitObligationFromGroupAnnuityContractPercent_5a20339f-25c4-4c0e-a09d-314acac148d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1_ceb4f5f0-ba4a-42cb-86fe-7cedca627ceb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1_ceb4f5f0-ba4a-42cb-86fe-7cedca627ceb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_927f14fe-a560-44dd-aadc-d345a80f1994" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanActuarialGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_927f14fe-a560-44dd-aadc-d345a80f1994" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid_a04f0993-3a9a-418d-998d-cbf8534afc79" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid_a04f0993-3a9a-418d-998d-cbf8534afc79" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation_ff530e7f-b94c-4cfa-8d08-8b82155c847e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation_ff530e7f-b94c-4cfa-8d08-8b82155c847e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear_5f8c8769-f083-452e-ba07-49e19f64f8ba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear_5f8c8769-f083-452e-ba07-49e19f64f8ba" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_DefinedBenefitPlanExpectedDirectPaymentsNextFiscalYear_ef8431e8-ab23-4096-8533-35f186940106" xlink:href="lfus-20201226.xsd#lfus_DefinedBenefitPlanExpectedDirectPaymentsNextFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_lfus_DefinedBenefitPlanExpectedDirectPaymentsNextFiscalYear_ef8431e8-ab23-4096-8533-35f186940106" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementBenefitExpense_64619491-47aa-49ff-85b7-3a2bf910c7fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionAndOtherPostretirementBenefitExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_us-gaap_PensionAndOtherPostretirementBenefitExpense_64619491-47aa-49ff-85b7-3a2bf910c7fe" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligation_c594c1db-025c-41ac-b10f-9c248c7bebf6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligation_c594c1db-025c-41ac-b10f-9c248c7bebf6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax_361b7d5d-dbdd-4074-8885-1a65bd3f0d75" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax_361b7d5d-dbdd-4074-8885-1a65bd3f0d75" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_57460454-682e-4b16-85aa-ac5294a5e5ac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_965d08f1-a3d9-4c7d-94a1-729d4b45146c" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_57460454-682e-4b16-85aa-ac5294a5e5ac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_8e77c2b8-1be4-44f3-9726-5c23692d6ca4" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_57460454-682e-4b16-85aa-ac5294a5e5ac" xlink:to="loc_srt_RangeAxis_8e77c2b8-1be4-44f3-9726-5c23692d6ca4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_8e77c2b8-1be4-44f3-9726-5c23692d6ca4_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_8e77c2b8-1be4-44f3-9726-5c23692d6ca4" xlink:to="loc_srt_RangeMember_8e77c2b8-1be4-44f3-9726-5c23692d6ca4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_4c778bd9-6a89-4596-a7f0-02ffa249745c" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_8e77c2b8-1be4-44f3-9726-5c23692d6ca4" xlink:to="loc_srt_RangeMember_4c778bd9-6a89-4596-a7f0-02ffa249745c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_45eda37e-30f3-47df-bae6-fe723f374219" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_4c778bd9-6a89-4596-a7f0-02ffa249745c" xlink:to="loc_srt_MinimumMember_45eda37e-30f3-47df-bae6-fe723f374219" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_cc5f94b3-eaa6-41c7-9f4a-64a6be92c1ab" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_4c778bd9-6a89-4596-a7f0-02ffa249745c" xlink:to="loc_srt_MaximumMember_cc5f94b3-eaa6-41c7-9f4a-64a6be92c1ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_bba1398c-aef6-41f5-bf6f-6f28c0a6cbce" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_57460454-682e-4b16-85aa-ac5294a5e5ac" xlink:to="loc_srt_StatementScenarioAxis_bba1398c-aef6-41f5-bf6f-6f28c0a6cbce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_bba1398c-aef6-41f5-bf6f-6f28c0a6cbce_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_bba1398c-aef6-41f5-bf6f-6f28c0a6cbce" xlink:to="loc_srt_ScenarioUnspecifiedDomain_bba1398c-aef6-41f5-bf6f-6f28c0a6cbce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_84c8f2dc-0060-4cf4-8658-edae077e391c" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_bba1398c-aef6-41f5-bf6f-6f28c0a6cbce" xlink:to="loc_srt_ScenarioUnspecifiedDomain_84c8f2dc-0060-4cf4-8658-edae077e391c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_8a0c9e53-8a66-49a4-af08-c468d13272b8" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_84c8f2dc-0060-4cf4-8658-edae077e391c" xlink:to="loc_srt_ScenarioForecastMember_8a0c9e53-8a66-49a4-af08-c468d13272b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_aec15995-2093-4fc6-85ac-8ffd1f21c4af" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_57460454-682e-4b16-85aa-ac5294a5e5ac" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_aec15995-2093-4fc6-85ac-8ffd1f21c4af" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_aec15995-2093-4fc6-85ac-8ffd1f21c4af_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_aec15995-2093-4fc6-85ac-8ffd1f21c4af" xlink:to="loc_us-gaap_EquityComponentDomain_aec15995-2093-4fc6-85ac-8ffd1f21c4af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_472246c5-ab54-4d00-ace2-87ccd83b881f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_aec15995-2093-4fc6-85ac-8ffd1f21c4af" xlink:to="loc_us-gaap_EquityComponentDomain_472246c5-ab54-4d00-ace2-87ccd83b881f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentAttributableToNoncontrollingInterestMember_20b193f9-88d2-4619-a573-4e3c6c714ed3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentAttributableToNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_472246c5-ab54-4d00-ace2-87ccd83b881f" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentAttributableToNoncontrollingInterestMember_20b193f9-88d2-4619-a573-4e3c6c714ed3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanSponsorLocationAxis_ac44fa8d-09c8-479b-9414-2fa65711f223" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanSponsorLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_57460454-682e-4b16-85aa-ac5294a5e5ac" xlink:to="loc_us-gaap_RetirementPlanSponsorLocationAxis_ac44fa8d-09c8-479b-9414-2fa65711f223" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanSponsorLocationDomain_ac44fa8d-09c8-479b-9414-2fa65711f223_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanSponsorLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanSponsorLocationAxis_ac44fa8d-09c8-479b-9414-2fa65711f223" xlink:to="loc_us-gaap_RetirementPlanSponsorLocationDomain_ac44fa8d-09c8-479b-9414-2fa65711f223_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanSponsorLocationDomain_f09e48d9-5d80-4e79-be7e-eeaf3c8e67ef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanSponsorLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanSponsorLocationAxis_ac44fa8d-09c8-479b-9414-2fa65711f223" xlink:to="loc_us-gaap_RetirementPlanSponsorLocationDomain_f09e48d9-5d80-4e79-be7e-eeaf3c8e67ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignPlanMember_10adb89e-dba4-417c-9fca-651324985569" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanSponsorLocationDomain_f09e48d9-5d80-4e79-be7e-eeaf3c8e67ef" xlink:to="loc_us-gaap_ForeignPlanMember_10adb89e-dba4-417c-9fca-651324985569" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_713b7db8-479b-469b-972f-abf4b1e4ba08" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_57460454-682e-4b16-85aa-ac5294a5e5ac" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_713b7db8-479b-469b-972f-abf4b1e4ba08" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_713b7db8-479b-469b-972f-abf4b1e4ba08_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_713b7db8-479b-469b-972f-abf4b1e4ba08" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_713b7db8-479b-469b-972f-abf4b1e4ba08_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_89fa1da8-de17-4d72-8c27-fe2097cfe547" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_713b7db8-479b-469b-972f-abf4b1e4ba08" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_89fa1da8-de17-4d72-8c27-fe2097cfe547" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesMember_8660c456-f2cf-4351-b462-d60a792d30bd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_89fa1da8-de17-4d72-8c27-fe2097cfe547" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesMember_8660c456-f2cf-4351-b462-d60a792d30bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncurrentLiabilitiesMember_d75f87a0-ac37-46a2-bce7-9ae54ee6382b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherNoncurrentLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_89fa1da8-de17-4d72-8c27-fe2097cfe547" xlink:to="loc_us-gaap_OtherNoncurrentLiabilitiesMember_d75f87a0-ac37-46a2-bce7-9ae54ee6382b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansBenefitPlanRelatedInformationDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansBenefitPlanRelatedInformationDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansBenefitPlanRelatedInformationDetails" xlink:type="extended" id="if7cedad371fd4d4a806744777fbb8195_BenefitPlansBenefitPlanRelatedInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_45a76f51-a26e-4c29-b9ab-1fcf4440f7d3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_45a76f51-a26e-4c29-b9ab-1fcf4440f7d3" xlink:to="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligation_787ff4fd-bf2e-4769-b9cc-077e1366ad72" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligation_787ff4fd-bf2e-4769-b9cc-077e1366ad72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanServiceCost_7f4c651d-2eb9-4deb-84a4-2e5064ed1f04" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanServiceCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:to="loc_us-gaap_DefinedBenefitPlanServiceCost_7f4c651d-2eb9-4deb-84a4-2e5064ed1f04" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_e66a00e2-2896-4272-9eb1-47b9a7c0f4fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_e66a00e2-2896-4272-9eb1-47b9a7c0f4fd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_045cf5fb-7bfb-4b39-a257-3dc8b5cb4216" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanActuarialGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_045cf5fb-7bfb-4b39-a257-3dc8b5cb4216" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid_1dc078ed-f4ea-46c2-949c-860305ff0fd5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid_1dc078ed-f4ea-46c2-949c-860305ff0fd5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_DefinedBenefitPlanBenefitsPaidDirectlyByCompany_28b6db8d-3fce-431a-ad10-afb09e7fbcde" xlink:href="lfus-20201226.xsd#lfus_DefinedBenefitPlanBenefitsPaidDirectlyByCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:to="loc_lfus_DefinedBenefitPlanBenefitsPaidDirectlyByCompany_28b6db8d-3fce-431a-ad10-afb09e7fbcde" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligationPaymentForSettlement_249f3dbb-78a6-4443-824e-85340f24f372" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligationPaymentForSettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligationPaymentForSettlement_249f3dbb-78a6-4443-824e-85340f24f372" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation_d6e43fa3-6b85-44a8-aa5e-f719ada7cbc9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:to="loc_us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation_d6e43fa3-6b85-44a8-aa5e-f719ada7cbc9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanOtherChanges_36560a4a-6638-4243-8026-0d52ad907438" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanOtherChanges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_f86e1a11-4e0e-4bce-94c6-05df7f6dc9df" xlink:to="loc_us-gaap_DefinedBenefitPlanOtherChanges_36560a4a-6638-4243-8026-0d52ad907438" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligation_64b72bb7-1135-4cb9-9204-4bdc222b3bd9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligation"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_fcbbbadc-7e68-4852-b8a9-0c0aa238f60c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_45a76f51-a26e-4c29-b9ab-1fcf4440f7d3" xlink:to="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_fcbbbadc-7e68-4852-b8a9-0c0aa238f60c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_f890de2e-9472-414c-85e1-99944b611e9d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_fcbbbadc-7e68-4852-b8a9-0c0aa238f60c" xlink:to="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_f890de2e-9472-414c-85e1-99944b611e9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets_a674e923-c97e-4ad2-97c7-1cdad2846f5e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_fcbbbadc-7e68-4852-b8a9-0c0aa238f60c" xlink:to="loc_us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets_a674e923-c97e-4ad2-97c7-1cdad2846f5e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_0641dd84-79d4-405e-8eb8-136218f9a4af" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanContributionsByEmployer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_fcbbbadc-7e68-4852-b8a9-0c0aa238f60c" xlink:to="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_0641dd84-79d4-405e-8eb8-136218f9a4af" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanPlanAssetsBenefitsPaid_667efaed-f8d5-4dd8-a805-874fe5d9d0a0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsBenefitsPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_fcbbbadc-7e68-4852-b8a9-0c0aa238f60c" xlink:to="loc_us-gaap_DefinedBenefitPlanPlanAssetsBenefitsPaid_667efaed-f8d5-4dd8-a805-874fe5d9d0a0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanSettlementsPlanAssets_67fd1ba4-3696-4e68-a902-8f83ef12482f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanSettlementsPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_fcbbbadc-7e68-4852-b8a9-0c0aa238f60c" xlink:to="loc_us-gaap_DefinedBenefitPlanSettlementsPlanAssets_67fd1ba4-3696-4e68-a902-8f83ef12482f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanPlanAssetsForeignCurrencyTranslationGainLoss_660b3e19-0afc-4660-8fc8-ffb97f1ec30b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_fcbbbadc-7e68-4852-b8a9-0c0aa238f60c" xlink:to="loc_us-gaap_DefinedBenefitPlanPlanAssetsForeignCurrencyTranslationGainLoss_660b3e19-0afc-4660-8fc8-ffb97f1ec30b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_9924c492-4d3d-424b-a817-4914d1d77b43" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFundedStatusOfPlan_b6ace2db-8b49-48d7-a8ed-7fc86f0f42fb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFundedStatusOfPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_fcbbbadc-7e68-4852-b8a9-0c0aa238f60c" xlink:to="loc_us-gaap_DefinedBenefitPlanFundedStatusOfPlan_b6ace2db-8b49-48d7-a8ed-7fc86f0f42fb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract_19f814d0-1d8d-4316-8f88-0ac33f17e5ea" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_45a76f51-a26e-4c29-b9ab-1fcf4440f7d3" xlink:to="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract_19f814d0-1d8d-4316-8f88-0ac33f17e5ea" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_99163dda-b345-4128-b9e5-75d17075c314" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract_19f814d0-1d8d-4316-8f88-0ac33f17e5ea" xlink:to="loc_us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_99163dda-b345-4128-b9e5-75d17075c314" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities_6dc3db24-199e-48a0-b8bf-1786d2ef6457" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract_19f814d0-1d8d-4316-8f88-0ac33f17e5ea" xlink:to="loc_us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities_6dc3db24-199e-48a0-b8bf-1786d2ef6457" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent_c211654b-eeca-45b5-89e8-d047986b11b3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract_19f814d0-1d8d-4316-8f88-0ac33f17e5ea" xlink:to="loc_us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent_c211654b-eeca-45b5-89e8-d047986b11b3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheet_8714a878-73c9-4fca-bbf0-1fd2db62eaa1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract_19f814d0-1d8d-4316-8f88-0ac33f17e5ea" xlink:to="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheet_8714a878-73c9-4fca-bbf0-1fd2db62eaa1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_898b591b-263c-4c37-b7a0-58d81431fae0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_45a76f51-a26e-4c29-b9ab-1fcf4440f7d3" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_898b591b-263c-4c37-b7a0-58d81431fae0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_078653cf-c2d7-4f7e-b053-91ef2550c1c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_898b591b-263c-4c37-b7a0-58d81431fae0" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_078653cf-c2d7-4f7e-b053-91ef2550c1c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_078653cf-c2d7-4f7e-b053-91ef2550c1c5_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_078653cf-c2d7-4f7e-b053-91ef2550c1c5" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_078653cf-c2d7-4f7e-b053-91ef2550c1c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_d78b76d0-e857-4c87-b31d-f74dcb1e9f4b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_078653cf-c2d7-4f7e-b053-91ef2550c1c5" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_d78b76d0-e857-4c87-b31d-f74dcb1e9f4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_26ddc354-b289-407e-bb3c-85bb6b6f5ff8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_d78b76d0-e857-4c87-b31d-f74dcb1e9f4b" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_26ddc354-b289-407e-bb3c-85bb6b6f5ff8" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansAmountsRecognizedinAccumulatedOtherComprehensiveIncomeLossPretaxDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansAmountsRecognizedinAccumulatedOtherComprehensiveIncomeLossPretaxDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansAmountsRecognizedinAccumulatedOtherComprehensiveIncomeLossPretaxDetails" xlink:type="extended" id="i924913b20d0e4af89b08c772633bf225_BenefitPlansAmountsRecognizedinAccumulatedOtherComprehensiveIncomeLossPretaxDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansBenefitPlanExpensesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansBenefitPlanExpensesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansBenefitPlanExpensesDetails" xlink:type="extended" id="id3949e50bd514e63a154b84e9a154c97_BenefitPlansBenefitPlanExpensesDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansWeightedAverageAssumptionsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansWeightedAverageAssumptionsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansWeightedAverageAssumptionsDetails" xlink:type="extended" id="i603d6314f8e14041b6d8d2e2fd8911ac_BenefitPlansWeightedAverageAssumptionsDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansFundedStatusofPlansDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansFundedStatusofPlansDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansFundedStatusofPlansDetails" xlink:type="extended" id="i3e83d24eeaa043c1901c21134131d3df_BenefitPlansFundedStatusofPlansDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansExpectedBenefitPaymentstoBePaidtoParticipantsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansExpectedBenefitPaymentstoBePaidtoParticipantsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansExpectedBenefitPaymentstoBePaidtoParticipantsDetails" xlink:type="extended" id="i72b319d948da4dfcb5e4a8f36174c44f_BenefitPlansExpectedBenefitPaymentstoBePaidtoParticipantsDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansAllocationofPlanAssetsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansAllocationofPlanAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansAllocationofPlanAssetsDetails" xlink:type="extended" id="i7a98cbc18f5f4811ba17db11545b478e_BenefitPlansAllocationofPlanAssetsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_c34f6632-8bea-4b97-b6d9-0a04197d1544" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations_c905183d-d127-41c1-b953-331a36884bd6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_c34f6632-8bea-4b97-b6d9-0a04197d1544" xlink:to="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations_c905183d-d127-41c1-b953-331a36884bd6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_a84055f1-f34c-42eb-a404-e756c4125689" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_c34f6632-8bea-4b97-b6d9-0a04197d1544" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_a84055f1-f34c-42eb-a404-e756c4125689" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_2018911b-8a43-484f-acef-61c551ee07ca" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_a84055f1-f34c-42eb-a404-e756c4125689" xlink:to="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_2018911b-8a43-484f-acef-61c551ee07ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanAssetCategoriesDomain_2018911b-8a43-484f-acef-61c551ee07ca_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanAssetCategoriesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_2018911b-8a43-484f-acef-61c551ee07ca" xlink:to="loc_us-gaap_PlanAssetCategoriesDomain_2018911b-8a43-484f-acef-61c551ee07ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanAssetCategoriesDomain_b3b43d13-0758-4bc9-9e2c-2b28029d0b1a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanAssetCategoriesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_2018911b-8a43-484f-acef-61c551ee07ca" xlink:to="loc_us-gaap_PlanAssetCategoriesDomain_b3b43d13-0758-4bc9-9e2c-2b28029d0b1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember_31860282-977d-4343-aa63-1074192c7a7f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_b3b43d13-0758-4bc9-9e2c-2b28029d0b1a" xlink:to="loc_us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember_31860282-977d-4343-aa63-1074192c7a7f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanEquitySecuritiesMember_2ca5d649-811b-46ac-a09b-a253656a2b8e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanEquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_b3b43d13-0758-4bc9-9e2c-2b28029d0b1a" xlink:to="loc_us-gaap_DefinedBenefitPlanEquitySecuritiesMember_2ca5d649-811b-46ac-a09b-a253656a2b8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedIncomeSecuritiesMember_71992951-b0a4-4c87-b5f8-4ddaf19db76f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FixedIncomeSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_b3b43d13-0758-4bc9-9e2c-2b28029d0b1a" xlink:to="loc_us-gaap_FixedIncomeSecuritiesMember_71992951-b0a4-4c87-b5f8-4ddaf19db76f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_BulkAnnuityContractMember_e4dd44e1-bfe7-48bf-b1bc-e58ca8b1c49c" xlink:href="lfus-20201226.xsd#lfus_BulkAnnuityContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_b3b43d13-0758-4bc9-9e2c-2b28029d0b1a" xlink:to="loc_lfus_BulkAnnuityContractMember_e4dd44e1-bfe7-48bf-b1bc-e58ca8b1c49c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansTheCompanysPensionPlanAssetsMeasuredatFairValueDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansTheCompanysPensionPlanAssetsMeasuredatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansTheCompanysPensionPlanAssetsMeasuredatFairValueDetails" xlink:type="extended" id="ia8aa8dcfc9a449abb728a5d41f5f481b_BenefitPlansTheCompanysPensionPlanAssetsMeasuredatFairValueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_342e6a7c-efc8-4c76-a9e9-02db25b2ecbb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_24665e0a-2f64-440c-93f9-2c2aebc28d3a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_342e6a7c-efc8-4c76-a9e9-02db25b2ecbb" xlink:to="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_24665e0a-2f64-440c-93f9-2c2aebc28d3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_98dbe4d0-1f6e-4d8e-bab8-86b40c7040ab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_342e6a7c-efc8-4c76-a9e9-02db25b2ecbb" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_98dbe4d0-1f6e-4d8e-bab8-86b40c7040ab" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_481f5779-73ab-4912-a051-f01895751daa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_98dbe4d0-1f6e-4d8e-bab8-86b40c7040ab" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_481f5779-73ab-4912-a051-f01895751daa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_481f5779-73ab-4912-a051-f01895751daa_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_481f5779-73ab-4912-a051-f01895751daa" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_481f5779-73ab-4912-a051-f01895751daa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_05ffbc2b-cc22-475b-b16d-cb5d976abb75" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_481f5779-73ab-4912-a051-f01895751daa" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_05ffbc2b-cc22-475b-b16d-cb5d976abb75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_b5aacab6-af92-4943-9786-ec897b824d28" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_05ffbc2b-cc22-475b-b16d-cb5d976abb75" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_b5aacab6-af92-4943-9786-ec897b824d28" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_b81852cd-3f91-4b2b-9a72-26e8592c3a67" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_05ffbc2b-cc22-475b-b16d-cb5d976abb75" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_b81852cd-3f91-4b2b-9a72-26e8592c3a67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_774d1f48-5f7e-4751-a82a-913c83180efe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_05ffbc2b-cc22-475b-b16d-cb5d976abb75" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_774d1f48-5f7e-4751-a82a-913c83180efe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember_e2965f5f-5133-4606-a72b-5ccbc96b1b32" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_05ffbc2b-cc22-475b-b16d-cb5d976abb75" xlink:to="loc_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember_e2965f5f-5133-4606-a72b-5ccbc96b1b32" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_e95da7e0-aefb-49c8-bcc7-729147b4be3e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_98dbe4d0-1f6e-4d8e-bab8-86b40c7040ab" xlink:to="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_e95da7e0-aefb-49c8-bcc7-729147b4be3e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanAssetCategoriesDomain_e95da7e0-aefb-49c8-bcc7-729147b4be3e_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanAssetCategoriesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_e95da7e0-aefb-49c8-bcc7-729147b4be3e" xlink:to="loc_us-gaap_PlanAssetCategoriesDomain_e95da7e0-aefb-49c8-bcc7-729147b4be3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanAssetCategoriesDomain_6c6581e4-a6e1-46a2-ab76-5fd7518a5263" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanAssetCategoriesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_e95da7e0-aefb-49c8-bcc7-729147b4be3e" xlink:to="loc_us-gaap_PlanAssetCategoriesDomain_6c6581e4-a6e1-46a2-ab76-5fd7518a5263" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_DefinedBenefitPlanInsuranceContractsandOtherMember_5afdee8d-dd26-4cc2-9e00-6867ba47abc8" xlink:href="lfus-20201226.xsd#lfus_DefinedBenefitPlanInsuranceContractsandOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_6c6581e4-a6e1-46a2-ab76-5fd7518a5263" xlink:to="loc_lfus_DefinedBenefitPlanInsuranceContractsandOtherMember_5afdee8d-dd26-4cc2-9e00-6867ba47abc8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember_0ceb327a-d6d2-4f42-976d-9c4b7700ddaf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_6c6581e4-a6e1-46a2-ab76-5fd7518a5263" xlink:to="loc_us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember_0ceb327a-d6d2-4f42-976d-9c4b7700ddaf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanEquitySecuritiesMember_bc2369f8-f498-4893-ae5c-054d5561d267" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanEquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_6c6581e4-a6e1-46a2-ab76-5fd7518a5263" xlink:to="loc_us-gaap_DefinedBenefitPlanEquitySecuritiesMember_bc2369f8-f498-4893-ae5c-054d5561d267" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDebtSecurityMember_835051bb-51f9-4d9f-a37a-bdcb83ef7dc9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDebtSecurityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_6c6581e4-a6e1-46a2-ab76-5fd7518a5263" xlink:to="loc_us-gaap_DefinedBenefitPlanDebtSecurityMember_835051bb-51f9-4d9f-a37a-bdcb83ef7dc9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_BulkAnnuityContractMember_ff5b417b-e70d-4939-9c0a-233419aa12e2" xlink:href="lfus-20201226.xsd#lfus_BulkAnnuityContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_6c6581e4-a6e1-46a2-ab76-5fd7518a5263" xlink:to="loc_lfus_BulkAnnuityContractMember_ff5b417b-e70d-4939-9c0a-233419aa12e2" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansFairValueMeasurementofPlanAssetsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansFairValueMeasurementofPlanAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansFairValueMeasurementofPlanAssetsDetails" xlink:type="extended" id="ia99e2d2f993a4935bab6cd69074be44c_BenefitPlansFairValueMeasurementofPlanAssetsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_3b82239a-5012-4db1-b19a-26b722a22219" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsLevel3ReconciliationRollForward_08034f23-c7d0-443c-961f-1ad66f92429f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsLevel3ReconciliationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_3b82239a-5012-4db1-b19a-26b722a22219" xlink:to="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsLevel3ReconciliationRollForward_08034f23-c7d0-443c-961f-1ad66f92429f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_c4def760-8a41-4f4d-9634-45f1cf8cf86e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsLevel3ReconciliationRollForward_08034f23-c7d0-443c-961f-1ad66f92429f" xlink:to="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_c4def760-8a41-4f4d-9634-45f1cf8cf86e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanPlanAssetsLevel3ReconciliationIncreaseForPurchase_6e93e7d3-0e9b-4132-86cb-809380e10279" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsLevel3ReconciliationIncreaseForPurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsLevel3ReconciliationRollForward_08034f23-c7d0-443c-961f-1ad66f92429f" xlink:to="loc_us-gaap_DefinedBenefitPlanPlanAssetsLevel3ReconciliationIncreaseForPurchase_6e93e7d3-0e9b-4132-86cb-809380e10279" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActualReturnOnPlanAssetsStillHeld_4fdeaa64-b220-47b8-9b79-c01d8b60e86e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanActualReturnOnPlanAssetsStillHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsLevel3ReconciliationRollForward_08034f23-c7d0-443c-961f-1ad66f92429f" xlink:to="loc_us-gaap_DefinedBenefitPlanActualReturnOnPlanAssetsStillHeld_4fdeaa64-b220-47b8-9b79-c01d8b60e86e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_25c49d5c-c0ec-479c-a638-557cac5fc022" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ef50db77-8e41-4bfd-8cf3-7d02265a8c1c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_3b82239a-5012-4db1-b19a-26b722a22219" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ef50db77-8e41-4bfd-8cf3-7d02265a8c1c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b8bbf104-791e-42c9-8df5-2d341544f91b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ef50db77-8e41-4bfd-8cf3-7d02265a8c1c" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b8bbf104-791e-42c9-8df5-2d341544f91b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b8bbf104-791e-42c9-8df5-2d341544f91b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b8bbf104-791e-42c9-8df5-2d341544f91b" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b8bbf104-791e-42c9-8df5-2d341544f91b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_65151bdc-0134-4ce2-b75a-9bb18c528f95" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b8bbf104-791e-42c9-8df5-2d341544f91b" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_65151bdc-0134-4ce2-b75a-9bb18c528f95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_70da69df-4cd2-4339-99f8-a01eb98bc783" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_65151bdc-0134-4ce2-b75a-9bb18c528f95" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_70da69df-4cd2-4339-99f8-a01eb98bc783" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/BenefitPlansDefinedContributionandOtherPlansDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#BenefitPlansDefinedContributionandOtherPlansDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/BenefitPlansDefinedContributionandOtherPlansDetails" xlink:type="extended" id="ic2f673b9c37b44e49236fbd1b2d0c0d2_BenefitPlansDefinedContributionandOtherPlansDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_9f613ad0-dfcf-4c70-9ed2-a12cbc5daf30" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch_b4c8d392-3c16-4621-8455-87ac108b6eb5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_9f613ad0-dfcf-4c70-9ed2-a12cbc5daf30" xlink:to="loc_us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch_b4c8d392-3c16-4621-8455-87ac108b6eb5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent_87c31ef2-b765-40c1-9ddb-223fc5e97349" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_9f613ad0-dfcf-4c70-9ed2-a12cbc5daf30" xlink:to="loc_us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent_87c31ef2-b765-40c1-9ddb-223fc5e97349" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_DefinedContributionPlanEmployerDiscretionaryMatchingContributionPercentOfEmployeesGrossPay_b3eff74b-45d4-472c-9691-3609e94907f7" xlink:href="lfus-20201226.xsd#lfus_DefinedContributionPlanEmployerDiscretionaryMatchingContributionPercentOfEmployeesGrossPay"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_9f613ad0-dfcf-4c70-9ed2-a12cbc5daf30" xlink:to="loc_lfus_DefinedContributionPlanEmployerDiscretionaryMatchingContributionPercentOfEmployeesGrossPay_b3eff74b-45d4-472c-9691-3609e94907f7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount_ac65a3cb-5ee7-438e-a3f1-da05ec92ec1b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_9f613ad0-dfcf-4c70-9ed2-a12cbc5daf30" xlink:to="loc_us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount_ac65a3cb-5ee7-438e-a3f1-da05ec92ec1b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability_0aef364f-7d17-4217-8049-bdb9b67aa9e7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_9f613ad0-dfcf-4c70-9ed2-a12cbc5daf30" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability_0aef364f-7d17-4217-8049-bdb9b67aa9e7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_DefinedContributionPlanPlanAssets_08c14cbd-0bfb-412c-88c8-5f876769f00d" xlink:href="lfus-20201226.xsd#lfus_DefinedContributionPlanPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_9f613ad0-dfcf-4c70-9ed2-a12cbc5daf30" xlink:to="loc_lfus_DefinedContributionPlanPlanAssets_08c14cbd-0bfb-412c-88c8-5f876769f00d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanTable_79cefd58-ebd1-4750-bd62-26df14616222" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedContributionPlanDisclosureLineItems_9f613ad0-dfcf-4c70-9ed2-a12cbc5daf30" xlink:to="loc_us-gaap_DefinedContributionPlanTable_79cefd58-ebd1-4750-bd62-26df14616222" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_ca686d21-20a8-4d9d-aefa-62a36e790530" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DefinedContributionPlanTable_79cefd58-ebd1-4750-bd62-26df14616222" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_ca686d21-20a8-4d9d-aefa-62a36e790530" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_ca686d21-20a8-4d9d-aefa-62a36e790530_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_ca686d21-20a8-4d9d-aefa-62a36e790530" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_ca686d21-20a8-4d9d-aefa-62a36e790530_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_9e93d5f7-e9ce-40f7-8780-57ccdee265aa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_ca686d21-20a8-4d9d-aefa-62a36e790530" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_9e93d5f7-e9ce-40f7-8780-57ccdee265aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMember_8d10db65-a0bf-40c0-970b-5da134f9e5d8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_9e93d5f7-e9ce-40f7-8780-57ccdee265aa" xlink:to="loc_us-gaap_OtherAssetsMember_8d10db65-a0bf-40c0-970b-5da134f9e5d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_OtherLongtermLiabilitiesMember_38cb4ae3-e16c-4fd1-817c-62ec071a4549" xlink:href="lfus-20201226.xsd#lfus_OtherLongtermLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_9e93d5f7-e9ce-40f7-8780-57ccdee265aa" xlink:to="loc_lfus_OtherLongtermLiabilitiesMember_38cb4ae3-e16c-4fd1-817c-62ec071a4549" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_cd52dc6f-80dc-4758-9408-e5d49be92122" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DefinedContributionPlanTable_79cefd58-ebd1-4750-bd62-26df14616222" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_cd52dc6f-80dc-4758-9408-e5d49be92122" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_cd52dc6f-80dc-4758-9408-e5d49be92122_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_cd52dc6f-80dc-4758-9408-e5d49be92122" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_cd52dc6f-80dc-4758-9408-e5d49be92122_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_cc4f4c55-9ec9-4b98-aa35-98f4c5fe94a2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_cd52dc6f-80dc-4758-9408-e5d49be92122" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_cc4f4c55-9ec9-4b98-aa35-98f4c5fe94a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember_206580bc-e201-4ca8-8233-c1d0f0e82fbe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_cc4f4c55-9ec9-4b98-aa35-98f4c5fe94a2" xlink:to="loc_us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember_206580bc-e201-4ca8-8233-c1d0f0e82fbe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanNameAxis_731af778-312b-4362-aeb3-7049ee470c89" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DefinedContributionPlanTable_79cefd58-ebd1-4750-bd62-26df14616222" xlink:to="loc_us-gaap_RetirementPlanNameAxis_731af778-312b-4362-aeb3-7049ee470c89" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanNameDomain_731af778-312b-4362-aeb3-7049ee470c89_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanNameAxis_731af778-312b-4362-aeb3-7049ee470c89" xlink:to="loc_us-gaap_RetirementPlanNameDomain_731af778-312b-4362-aeb3-7049ee470c89_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanNameDomain_c4b9eb07-72ca-4538-9f82-c4567cfa0718" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanNameAxis_731af778-312b-4362-aeb3-7049ee470c89" xlink:to="loc_us-gaap_RetirementPlanNameDomain_c4b9eb07-72ca-4538-9f82-c4567cfa0718" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_SavingsPlan401KMember_a55bfe72-382f-4eb1-b65b-34fd083cb71c" xlink:href="lfus-20201226.xsd#lfus_SavingsPlan401KMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanNameDomain_c4b9eb07-72ca-4538-9f82-c4567cfa0718" xlink:to="loc_lfus_SavingsPlan401KMember_a55bfe72-382f-4eb1-b65b-34fd083cb71c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/StockBasedCompensation" xlink:type="simple" xlink:href="lfus-20201226.xsd#StockBasedCompensation"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/StockBasedCompensation" xlink:type="extended" id="i58892d3f1c2a43a3a3281183c53a208d_StockBasedCompensation"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/StockBasedCompensationTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#StockBasedCompensationTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/StockBasedCompensationTables" xlink:type="extended" id="i24560a2943d5475dbf611b6c3e277c31_StockBasedCompensationTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/StockBasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#StockBasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/StockBasedCompensationNarrativeDetails" xlink:type="extended" id="iccdf3c0d9bb24a21abb14585fca8880b_StockBasedCompensationNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_e1f0c13c-cb2b-478f-95cb-86dfad95adcf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_e1f0c13c-cb2b-478f-95cb-86dfad95adcf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_13dbdc5f-a87c-43e7-be7e-5eeff3963b81" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_13dbdc5f-a87c-43e7-be7e-5eeff3963b81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_4b03b99d-ea63-4ac2-b7e7-17a064700e39" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_4b03b99d-ea63-4ac2-b7e7-17a064700e39" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsConvertedinPeriod_85c269a8-029d-4a9b-b63b-6b0694dc9e4c" xlink:href="lfus-20201226.xsd#lfus_SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsConvertedinPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_lfus_SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsConvertedinPeriod_85c269a8-029d-4a9b-b63b-6b0694dc9e4c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_a0e22a6e-0741-4d83-80d7-c0978d23d940" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_a0e22a6e-0741-4d83-80d7-c0978d23d940" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_868455cd-584d-46f7-888e-d3b34cce2db1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_ShareBasedCompensation_868455cd-584d-46f7-888e-d3b34cce2db1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_7a2a1d99-1e69-469a-9fe5-1897d085b818" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_7a2a1d99-1e69-469a-9fe5-1897d085b818" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_f4708ad8-d7c5-491d-be28-d831010b3909" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_f4708ad8-d7c5-491d-be28-d831010b3909" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid_b19dad33-abbf-4ecb-9d0c-cf9b4ff5006c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid_b19dad33-abbf-4ecb-9d0c-cf9b4ff5006c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_b5d9ce07-5f15-48c0-8637-a1a421336967" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_b5d9ce07-5f15-48c0-8637-a1a421336967" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_c5a75790-7e7b-411e-a1dc-cfb55093859d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_c5a75790-7e7b-411e-a1dc-cfb55093859d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_237bd1f9-49b8-4a89-b966-bbd4cde7c9ab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_237bd1f9-49b8-4a89-b966-bbd4cde7c9ab" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased_4a8a4a04-c71b-47b4-aa22-42680cc3b11b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased_4a8a4a04-c71b-47b4-aa22-42680cc3b11b" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_39d02be6-34a2-4020-b146-593191d9b03b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_39d02be6-34a2-4020-b146-593191d9b03b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_0a624329-24cd-49ef-90b3-1ebde81e320d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_0a624329-24cd-49ef-90b3-1ebde81e320d" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ca2f084f-2c49-486e-ab40-b94538e7b8fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_a28cb258-1898-43ea-a00f-7f6db50727e1" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ca2f084f-2c49-486e-ab40-b94538e7b8fc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_00cb53be-e1d1-4470-b03a-7c940adef454" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ca2f084f-2c49-486e-ab40-b94538e7b8fc" xlink:to="loc_srt_RangeAxis_00cb53be-e1d1-4470-b03a-7c940adef454" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_00cb53be-e1d1-4470-b03a-7c940adef454_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_00cb53be-e1d1-4470-b03a-7c940adef454" xlink:to="loc_srt_RangeMember_00cb53be-e1d1-4470-b03a-7c940adef454_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f5bcc0a9-7544-4f58-9c7b-e2ed7fd47cc5" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_00cb53be-e1d1-4470-b03a-7c940adef454" xlink:to="loc_srt_RangeMember_f5bcc0a9-7544-4f58-9c7b-e2ed7fd47cc5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_710b10b7-0a0e-4c6d-9dd8-72fb5beca202" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f5bcc0a9-7544-4f58-9c7b-e2ed7fd47cc5" xlink:to="loc_srt_MinimumMember_710b10b7-0a0e-4c6d-9dd8-72fb5beca202" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_2bbbe872-0a87-4858-b7f4-ecd9d802f454" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f5bcc0a9-7544-4f58-9c7b-e2ed7fd47cc5" xlink:to="loc_srt_MaximumMember_2bbbe872-0a87-4858-b7f4-ecd9d802f454" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_727b553c-8421-4522-b8e9-02ff1e891c2a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ca2f084f-2c49-486e-ab40-b94538e7b8fc" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_727b553c-8421-4522-b8e9-02ff1e891c2a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_727b553c-8421-4522-b8e9-02ff1e891c2a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_727b553c-8421-4522-b8e9-02ff1e891c2a" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_727b553c-8421-4522-b8e9-02ff1e891c2a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_e0873386-cf36-4bf7-9fd4-3db09d5a995c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_727b553c-8421-4522-b8e9-02ff1e891c2a" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_e0873386-cf36-4bf7-9fd4-3db09d5a995c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IXYSCorporationMember_15a32101-58c3-44fa-ba07-4cd22750050b" xlink:href="lfus-20201226.xsd#lfus_IXYSCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_e0873386-cf36-4bf7-9fd4-3db09d5a995c" xlink:to="loc_lfus_IXYSCorporationMember_15a32101-58c3-44fa-ba07-4cd22750050b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_9909b371-9480-4173-91fa-e09e71f9238c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ca2f084f-2c49-486e-ab40-b94538e7b8fc" xlink:to="loc_us-gaap_AwardTypeAxis_9909b371-9480-4173-91fa-e09e71f9238c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9909b371-9480-4173-91fa-e09e71f9238c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_9909b371-9480-4173-91fa-e09e71f9238c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9909b371-9480-4173-91fa-e09e71f9238c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_65ba7e9a-8e6c-4e2a-8803-762931b6fd15" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_9909b371-9480-4173-91fa-e09e71f9238c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_65ba7e9a-8e6c-4e2a-8803-762931b6fd15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_45bb9a9c-7128-472a-a174-657d6af90a2a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_65ba7e9a-8e6c-4e2a-8803-762931b6fd15" xlink:to="loc_us-gaap_EmployeeStockOptionMember_45bb9a9c-7128-472a-a174-657d6af90a2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_RestrictedStockAndRestrictedShareUnitsMember_fd8c0de1-20bb-41b9-8ff3-e0fd66e1642e" xlink:href="lfus-20201226.xsd#lfus_RestrictedStockAndRestrictedShareUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_65ba7e9a-8e6c-4e2a-8803-762931b6fd15" xlink:to="loc_lfus_RestrictedStockAndRestrictedShareUnitsMember_fd8c0de1-20bb-41b9-8ff3-e0fd66e1642e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareRepurchaseProgramAxis_737035e2-8a93-4bc5-8197-87b89733e6d4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ca2f084f-2c49-486e-ab40-b94538e7b8fc" xlink:to="loc_us-gaap_ShareRepurchaseProgramAxis_737035e2-8a93-4bc5-8197-87b89733e6d4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_737035e2-8a93-4bc5-8197-87b89733e6d4_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_737035e2-8a93-4bc5-8197-87b89733e6d4" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_737035e2-8a93-4bc5-8197-87b89733e6d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_1d985367-bd4f-4e91-aece-60b3e2febe8c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_737035e2-8a93-4bc5-8197-87b89733e6d4" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_1d985367-bd4f-4e91-aece-60b3e2febe8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_A2018ShareRepurchaseProgramMember_559aece8-0eb0-46bc-ab72-94a50ab9ebbd" xlink:href="lfus-20201226.xsd#lfus_A2018ShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_1d985367-bd4f-4e91-aece-60b3e2febe8c" xlink:to="loc_lfus_A2018ShareRepurchaseProgramMember_559aece8-0eb0-46bc-ab72-94a50ab9ebbd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_A2019ShareRepurchaseProgramMember_a38e1cdc-728a-46b8-9e76-f4f6a8d6bb77" xlink:href="lfus-20201226.xsd#lfus_A2019ShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_1d985367-bd4f-4e91-aece-60b3e2febe8c" xlink:to="loc_lfus_A2019ShareRepurchaseProgramMember_a38e1cdc-728a-46b8-9e76-f4f6a8d6bb77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_A2020ShareRepurchaseProgramMember_73da1064-232a-473c-bac8-5aacf5dc1446" xlink:href="lfus-20201226.xsd#lfus_A2020ShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_1d985367-bd4f-4e91-aece-60b3e2febe8c" xlink:to="loc_lfus_A2020ShareRepurchaseProgramMember_73da1064-232a-473c-bac8-5aacf5dc1446" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/StockBasedCompensationReconciliationofOutstandingStockOptionsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#StockBasedCompensationReconciliationofOutstandingStockOptionsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/StockBasedCompensationReconciliationofOutstandingStockOptionsDetails" xlink:type="extended" id="idad29b7b264b4813a7e995f4a8857f78_StockBasedCompensationReconciliationofOutstandingStockOptionsDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/StockBasedCompensationReconciliationofNonvestedRestrictedShareandShareUnitAwardsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#StockBasedCompensationReconciliationofNonvestedRestrictedShareandShareUnitAwardsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/StockBasedCompensationReconciliationofNonvestedRestrictedShareandShareUnitAwardsDetails" xlink:type="extended" id="i59a878cd22c24199ab0ab6a610e4c07e_StockBasedCompensationReconciliationofNonvestedRestrictedShareandShareUnitAwardsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7b6c3d1e-e942-4cdf-86f4-368d55e677e6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_02435edb-9434-451f-b272-d70d575fedbd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7b6c3d1e-e942-4cdf-86f4-368d55e677e6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_02435edb-9434-451f-b272-d70d575fedbd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_fbf035e1-16ff-4a7c-8550-6dba8a0b51ae" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_02435edb-9434-451f-b272-d70d575fedbd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_fbf035e1-16ff-4a7c-8550-6dba8a0b51ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_b2e5f1ae-1d89-4881-b058-2242d821f5c9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_02435edb-9434-451f-b272-d70d575fedbd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_b2e5f1ae-1d89-4881-b058-2242d821f5c9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_239b975b-8e23-4b9e-a8cb-30958e571520" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_02435edb-9434-451f-b272-d70d575fedbd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_239b975b-8e23-4b9e-a8cb-30958e571520" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_820af20e-526e-403b-a136-64baf58e653f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_02435edb-9434-451f-b272-d70d575fedbd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_820af20e-526e-403b-a136-64baf58e653f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_a564af35-800b-4106-a901-f70729741f6e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7e43ed7c-5b5f-4db8-a6ed-43064dcaf9ce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7b6c3d1e-e942-4cdf-86f4-368d55e677e6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7e43ed7c-5b5f-4db8-a6ed-43064dcaf9ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_e159e0b1-6ace-4d8c-8519-f4fba9ace996" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7e43ed7c-5b5f-4db8-a6ed-43064dcaf9ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_e159e0b1-6ace-4d8c-8519-f4fba9ace996" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_08b30522-3b39-48c4-a2f0-6304a1c39af9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7e43ed7c-5b5f-4db8-a6ed-43064dcaf9ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_08b30522-3b39-48c4-a2f0-6304a1c39af9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_7224fde6-3545-49a2-9132-db394193bfa3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7e43ed7c-5b5f-4db8-a6ed-43064dcaf9ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_7224fde6-3545-49a2-9132-db394193bfa3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_35737a02-32ee-497f-a96e-cd754c5d0567" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7e43ed7c-5b5f-4db8-a6ed-43064dcaf9ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_35737a02-32ee-497f-a96e-cd754c5d0567" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_c7506bcb-6caa-4ef2-ae3a-b2340a9d066f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05e496a1-c286-4f5e-83f3-eeae97d0f533" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7b6c3d1e-e942-4cdf-86f4-368d55e677e6" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05e496a1-c286-4f5e-83f3-eeae97d0f533" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_0e544cf4-702d-4f29-a7b5-fb8a9b9e817a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05e496a1-c286-4f5e-83f3-eeae97d0f533" xlink:to="loc_us-gaap_AwardTypeAxis_0e544cf4-702d-4f29-a7b5-fb8a9b9e817a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0e544cf4-702d-4f29-a7b5-fb8a9b9e817a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_0e544cf4-702d-4f29-a7b5-fb8a9b9e817a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0e544cf4-702d-4f29-a7b5-fb8a9b9e817a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f0597f82-ecbf-4f67-9e1f-1fd12b4245dd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_0e544cf4-702d-4f29-a7b5-fb8a9b9e817a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f0597f82-ecbf-4f67-9e1f-1fd12b4245dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_RestrictedStockAndRestrictedShareUnitsMember_4b04b459-7fa8-45de-b6a4-e96504a94e57" xlink:href="lfus-20201226.xsd#lfus_RestrictedStockAndRestrictedShareUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f0597f82-ecbf-4f67-9e1f-1fd12b4245dd" xlink:to="loc_lfus_RestrictedStockAndRestrictedShareUnitsMember_4b04b459-7fa8-45de-b6a4-e96504a94e57" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/StockBasedCompensationWeightedAverageFairValueofOptionsGrantedandBlackScholesOptionValuationModelAssumptionsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#StockBasedCompensationWeightedAverageFairValueofOptionsGrantedandBlackScholesOptionValuationModelAssumptionsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/StockBasedCompensationWeightedAverageFairValueofOptionsGrantedandBlackScholesOptionValuationModelAssumptionsDetails" xlink:type="extended" id="ia17ecb396fbf4149893d2e60843da650_StockBasedCompensationWeightedAverageFairValueofOptionsGrantedandBlackScholesOptionValuationModelAssumptionsDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/OtherComprehensiveIncomeLoss" xlink:type="simple" xlink:href="lfus-20201226.xsd#OtherComprehensiveIncomeLoss"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/OtherComprehensiveIncomeLoss" xlink:type="extended" id="i60d4e0516fc74cb3bcd4f907afbdce76_OtherComprehensiveIncomeLoss"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/OtherComprehensiveIncomeLossTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#OtherComprehensiveIncomeLossTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/OtherComprehensiveIncomeLossTables" xlink:type="extended" id="i28a70d4763d9419998175f09aa0af019_OtherComprehensiveIncomeLossTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/OtherComprehensiveIncomeLossScheduleofComponentsofComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#OtherComprehensiveIncomeLossScheduleofComponentsofComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/OtherComprehensiveIncomeLossScheduleofComponentsofComprehensiveIncomeLossDetails" xlink:type="extended" id="i576dc06c47b442deb049dbdea9b979b4_OtherComprehensiveIncomeLossScheduleofComponentsofComprehensiveIncomeLossDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_695ce59e-6a6f-43b0-8deb-40168e0bcbcf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciNetOfTaxAbstract_60198aaf-7549-4711-90f2-be8e7b199690" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OciNetOfTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_695ce59e-6a6f-43b0-8deb-40168e0bcbcf" xlink:to="loc_us-gaap_OciNetOfTaxAbstract_60198aaf-7549-4711-90f2-be8e7b199690" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_9e5df175-d216-4617-97e3-f201ec3a6df6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OciNetOfTaxAbstract_60198aaf-7549-4711-90f2-be8e7b199690" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_9e5df175-d216-4617-97e3-f201ec3a6df6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_3ddf4d06-ab12-45e5-95e3-bfdc6f2a45a2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OciNetOfTaxAbstract_60198aaf-7549-4711-90f2-be8e7b199690" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTax_3ddf4d06-ab12-45e5-95e3-bfdc6f2a45a2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_ac87d7c8-dcfc-457d-a31f-52fdc0ca292c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OciNetOfTaxAbstract_60198aaf-7549-4711-90f2-be8e7b199690" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_ac87d7c8-dcfc-457d-a31f-52fdc0ca292c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_4074c22d-e58b-4a76-8eaa-7ef83e882499" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_695ce59e-6a6f-43b0-8deb-40168e0bcbcf" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_4074c22d-e58b-4a76-8eaa-7ef83e882499" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_28b11ee9-7990-4900-833f-290d2b8b9cec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_4074c22d-e58b-4a76-8eaa-7ef83e882499" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_28b11ee9-7990-4900-833f-290d2b8b9cec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_28b11ee9-7990-4900-833f-290d2b8b9cec_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_28b11ee9-7990-4900-833f-290d2b8b9cec" xlink:to="loc_us-gaap_EquityComponentDomain_28b11ee9-7990-4900-833f-290d2b8b9cec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_2fe8ae1a-539c-494a-a2bc-14356891fd60" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_28b11ee9-7990-4900-833f-290d2b8b9cec" xlink:to="loc_us-gaap_EquityComponentDomain_2fe8ae1a-539c-494a-a2bc-14356891fd60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_76e8ffce-df45-4288-aa15-5133105eeb2b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2fe8ae1a-539c-494a-a2bc-14356891fd60" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_76e8ffce-df45-4288-aa15-5133105eeb2b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_9c9f1d00-c7d9-4123-a560-0683d9da0fe1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2fe8ae1a-539c-494a-a2bc-14356891fd60" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_9c9f1d00-c7d9-4123-a560-0683d9da0fe1" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/OtherComprehensiveIncomeLossScheduleofAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#OtherComprehensiveIncomeLossScheduleofAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/OtherComprehensiveIncomeLossScheduleofAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended" id="i78aec140c470406ab656767974579c24_OtherComprehensiveIncomeLossScheduleofAccumulatedOtherComprehensiveIncomeLossDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_a8652f6a-4357-4e9a-84d3-5270b2efd203" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_da981a4b-efc4-4e2a-9dc7-a72b87a03c19" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_a8652f6a-4357-4e9a-84d3-5270b2efd203" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_da981a4b-efc4-4e2a-9dc7-a72b87a03c19" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_3856d365-46ae-4163-994c-d7772e091edb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_da981a4b-efc4-4e2a-9dc7-a72b87a03c19" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_3856d365-46ae-4163-994c-d7772e091edb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_de852591-c5b0-47b9-abca-ada89f530403" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_da981a4b-efc4-4e2a-9dc7-a72b87a03c19" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_de852591-c5b0-47b9-abca-ada89f530403" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_d50ebb9a-6e49-42d5-b59c-f1724b2c0e33" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_90749dd7-e61e-405c-995d-3f16fafaf9bc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_a8652f6a-4357-4e9a-84d3-5270b2efd203" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_90749dd7-e61e-405c-995d-3f16fafaf9bc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_fab6142b-96df-48ac-b580-f149631d6986" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_90749dd7-e61e-405c-995d-3f16fafaf9bc" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_fab6142b-96df-48ac-b580-f149631d6986" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_fab6142b-96df-48ac-b580-f149631d6986_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_fab6142b-96df-48ac-b580-f149631d6986" xlink:to="loc_us-gaap_EquityComponentDomain_fab6142b-96df-48ac-b580-f149631d6986_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_7de0b663-a2e7-43cd-9c9b-34b03358821f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_fab6142b-96df-48ac-b580-f149631d6986" xlink:to="loc_us-gaap_EquityComponentDomain_7de0b663-a2e7-43cd-9c9b-34b03358821f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_3e97d538-938c-4def-b9dc-2e65539ee3e7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_7de0b663-a2e7-43cd-9c9b-34b03358821f" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_3e97d538-938c-4def-b9dc-2e65539ee3e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_5462c6da-71d5-4895-ae0c-ff7bf1b715b0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_3e97d538-938c-4def-b9dc-2e65539ee3e7" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_5462c6da-71d5-4895-ae0c-ff7bf1b715b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_a30dfafd-4d75-41de-b9ff-20d2cf97d9a2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_3e97d538-938c-4def-b9dc-2e65539ee3e7" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_a30dfafd-4d75-41de-b9ff-20d2cf97d9a2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_69821e6d-c888-4fdc-a7cd-2b0affca4b82" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_3e97d538-938c-4def-b9dc-2e65539ee3e7" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_69821e6d-c888-4fdc-a7cd-2b0affca4b82" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_74e8e208-705d-4bb0-9d9b-9b2d1d3c61ee" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_90749dd7-e61e-405c-995d-3f16fafaf9bc" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_74e8e208-705d-4bb0-9d9b-9b2d1d3c61ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_74e8e208-705d-4bb0-9d9b-9b2d1d3c61ee_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_74e8e208-705d-4bb0-9d9b-9b2d1d3c61ee" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_74e8e208-705d-4bb0-9d9b-9b2d1d3c61ee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_99b20f0f-e26d-4a5a-a442-4417a3febc52" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_74e8e208-705d-4bb0-9d9b-9b2d1d3c61ee" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_99b20f0f-e26d-4a5a-a442-4417a3febc52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_725f10f2-0470-4384-88e7-ce0c9abb31b8" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_99b20f0f-e26d-4a5a-a442-4417a3febc52" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_725f10f2-0470-4384-88e7-ce0c9abb31b8" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/OtherComprehensiveIncomeLossReclassificationoutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#OtherComprehensiveIncomeLossReclassificationoutofAccumulatedOtherComprehensiveIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/OtherComprehensiveIncomeLossReclassificationoutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended" id="i0c1f8a480e19464c9d79b889a0d3337d_OtherComprehensiveIncomeLossReclassificationoutofAccumulatedOtherComprehensiveIncomeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_eb0268b6-376b-4c69-9ea9-30013c684b97" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIncome_5ea50723-b889-4f10-961b-fc9b3bf188d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_eb0268b6-376b-4c69-9ea9-30013c684b97" xlink:to="loc_us-gaap_OtherIncome_5ea50723-b889-4f10-961b-fc9b3bf188d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_6c0f4263-0eed-474e-8930-fb2b3401835b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_eb0268b6-376b-4c69-9ea9-30013c684b97" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_6c0f4263-0eed-474e-8930-fb2b3401835b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_25c046dd-d74e-417e-a9ca-aedf61122e1f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_6c0f4263-0eed-474e-8930-fb2b3401835b" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_25c046dd-d74e-417e-a9ca-aedf61122e1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_25c046dd-d74e-417e-a9ca-aedf61122e1f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_25c046dd-d74e-417e-a9ca-aedf61122e1f" xlink:to="loc_us-gaap_EquityComponentDomain_25c046dd-d74e-417e-a9ca-aedf61122e1f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ab82e1df-2b81-46b9-a323-d267abd5385f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_25c046dd-d74e-417e-a9ca-aedf61122e1f" xlink:to="loc_us-gaap_EquityComponentDomain_ab82e1df-2b81-46b9-a323-d267abd5385f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceIncludingPortionAttributableToNoncontrollingInterestMember_7767020a-f9c7-414c-bc6a-e9b46996f797" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceIncludingPortionAttributableToNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ab82e1df-2b81-46b9-a323-d267abd5385f" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceIncludingPortionAttributableToNoncontrollingInterestMember_7767020a-f9c7-414c-bc6a-e9b46996f797" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetGainLossIncludingPortionAttributableToNoncontrollingInterestMember_11330e54-ab2e-4313-bb3b-f4cc8e9ca86b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetGainLossIncludingPortionAttributableToNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ab82e1df-2b81-46b9-a323-d267abd5385f" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetGainLossIncludingPortionAttributableToNoncontrollingInterestMember_11330e54-ab2e-4313-bb3b-f4cc8e9ca86b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_47b35cf6-7324-46d9-b846-06915f6af3e3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_6c0f4263-0eed-474e-8930-fb2b3401835b" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_47b35cf6-7324-46d9-b846-06915f6af3e3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_47b35cf6-7324-46d9-b846-06915f6af3e3_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_47b35cf6-7324-46d9-b846-06915f6af3e3" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_47b35cf6-7324-46d9-b846-06915f6af3e3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_0c959ef9-8af4-47e0-82b2-53ecc50b8c9a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_47b35cf6-7324-46d9-b846-06915f6af3e3" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_0c959ef9-8af4-47e0-82b2-53ecc50b8c9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_90c66676-4738-4b4c-84af-22f07f1ee7c2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_0c959ef9-8af4-47e0-82b2-53ecc50b8c9a" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_90c66676-4738-4b4c-84af-22f07f1ee7c2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/IncomeTaxes" xlink:type="simple" xlink:href="lfus-20201226.xsd#IncomeTaxes"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/IncomeTaxes" xlink:type="extended" id="i0f963ada447d4004ac33583dcc953717_IncomeTaxes"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/IncomeTaxesTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#IncomeTaxesTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/IncomeTaxesTables" xlink:type="extended" id="ica283bc5b6024e718ae26b8ff8934a70_IncomeTaxesTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/IncomeTaxesNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#IncomeTaxesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/IncomeTaxesNarrativeDetails" xlink:type="extended" id="icaa2186eb38747939cfda4386a885c10_IncomeTaxesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit_0f503da6-c7e3-4b5c-baa6-7b033e50e643" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit_0f503da6-c7e3-4b5c-baa6-7b033e50e643" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiabilityTollChargeNoncurrent_3fe5d07a-71e6-4e10-9914-586c33a1d056" xlink:href="lfus-20201226.xsd#lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiabilityTollChargeNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiabilityTollChargeNoncurrent_3fe5d07a-71e6-4e10-9914-586c33a1d056" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentofDeferredTaxAssetLiabilityTollChargeCurrent_6c24e463-cb13-4d30-bd93-29337659aa24" xlink:href="lfus-20201226.xsd#lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentofDeferredTaxAssetLiabilityTollChargeCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_lfus_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentofDeferredTaxAssetLiabilityTollChargeCurrent_6c24e463-cb13-4d30-bd93-29337659aa24" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease_62f987e6-a819-4870-801a-e0b626c4ba3d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease_62f987e6-a819-4870-801a-e0b626c4ba3d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaid_5bd400df-5608-4fb2-a70b-df8872361d19" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxesPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_us-gaap_IncomeTaxesPaid_5bd400df-5608-4fb2-a70b-df8872361d19" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIncomeTaxRefunds_f3be71f0-c2e1-4025-a0a7-0cbff14a11cd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIncomeTaxRefunds"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_us-gaap_ProceedsFromIncomeTaxRefunds_f3be71f0-c2e1-4025-a0a7-0cbff14a11cd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsOfForeignSubsidiaries_0c7a50e9-1331-4507-a05d-7b7f44810149" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UndistributedEarningsOfForeignSubsidiaries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_us-gaap_UndistributedEarningsOfForeignSubsidiaries_0c7a50e9-1331-4507-a05d-7b7f44810149" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_DeferredTaxLiabilitiesRecognizedonUndistributedForeignEarnings_672760ca-e44e-474b-85eb-8b728442eff9" xlink:href="lfus-20201226.xsd#lfus_DeferredTaxLiabilitiesRecognizedonUndistributedForeignEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_lfus_DeferredTaxLiabilitiesRecognizedonUndistributedForeignEarnings_672760ca-e44e-474b-85eb-8b728442eff9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxHolidayAggregateDollarAmount_15f41379-2c1b-4e5e-bd22-49041e8f5de2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxHolidayAggregateDollarAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_us-gaap_IncomeTaxHolidayAggregateDollarAmount_15f41379-2c1b-4e5e-bd22-49041e8f5de2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IncomeTaxHolidayExpenseBenefitAmountPerDilutedShare_dcee738f-4ea4-477c-bf19-a495dca35f0e" xlink:href="lfus-20201226.xsd#lfus_IncomeTaxHolidayExpenseBenefitAmountPerDilutedShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_lfus_IncomeTaxHolidayExpenseBenefitAmountPerDilutedShare_dcee738f-4ea4-477c-bf19-a495dca35f0e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExaminationInterestExpense_2f840df1-93dd-42f1-93e8-97adb145f167" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExaminationInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_us-gaap_IncomeTaxExaminationInterestExpense_2f840df1-93dd-42f1-93e8-97adb145f167" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IncomeTaxExaminationDecreaseDuetoLapseofStatuteofLimitations_bf720fc8-7082-4d68-85b4-d2b67e9c9844" xlink:href="lfus-20201226.xsd#lfus_IncomeTaxExaminationDecreaseDuetoLapseofStatuteofLimitations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_lfus_IncomeTaxExaminationDecreaseDuetoLapseofStatuteofLimitations_bf720fc8-7082-4d68-85b4-d2b67e9c9844" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExaminationInterestAccrued_bf32db11-f957-405d-abcf-ebbb442f0ac1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExaminationInterestAccrued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_us-gaap_IncomeTaxExaminationInterestAccrued_bf32db11-f957-405d-abcf-ebbb442f0ac1" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_1be68e3b-2d43-4fc0-a626-9e45e532f83e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecognizedTaxBenefits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_1be68e3b-2d43-4fc0-a626-9e45e532f83e" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_PotentialTaxCharges_2b7843f6-7116-4427-9ce2-1c00995f486d" xlink:href="lfus-20201226.xsd#lfus_PotentialTaxCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_lfus_PotentialTaxCharges_2b7843f6-7116-4427-9ce2-1c00995f486d" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyTable_0370ac00-5c7e-4755-95cc-2ede9fd32e2a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_581340cd-1ce0-4eec-8804-4f2d833adb0a" xlink:to="loc_us-gaap_IncomeTaxContingencyTable_0370ac00-5c7e-4755-95cc-2ede9fd32e2a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodAxis_385302d1-f29c-412b-8032-d79527cbe662" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_0370ac00-5c7e-4755-95cc-2ede9fd32e2a" xlink:to="loc_us-gaap_TaxPeriodAxis_385302d1-f29c-412b-8032-d79527cbe662" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_385302d1-f29c-412b-8032-d79527cbe662_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TaxPeriodAxis_385302d1-f29c-412b-8032-d79527cbe662" xlink:to="loc_us-gaap_TaxPeriodDomain_385302d1-f29c-412b-8032-d79527cbe662_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_e040abc1-e3df-4bbe-95f9-9fa3eed4ef8a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TaxPeriodAxis_385302d1-f29c-412b-8032-d79527cbe662" xlink:to="loc_us-gaap_TaxPeriodDomain_e040abc1-e3df-4bbe-95f9-9fa3eed4ef8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_TollChargeMember_60684bc8-a29f-4abd-a781-356aeb0e0ca2" xlink:href="lfus-20201226.xsd#lfus_TollChargeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxPeriodDomain_e040abc1-e3df-4bbe-95f9-9fa3eed4ef8a" xlink:to="loc_lfus_TollChargeMember_60684bc8-a29f-4abd-a781-356aeb0e0ca2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_OtherItemsMember_00028bbc-c0d6-44ae-85de-a64b6696fa26" xlink:href="lfus-20201226.xsd#lfus_OtherItemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxPeriodDomain_e040abc1-e3df-4bbe-95f9-9fa3eed4ef8a" xlink:to="loc_lfus_OtherItemsMember_00028bbc-c0d6-44ae-85de-a64b6696fa26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_5906e244-abf6-4883-9586-9b4ec3d74cee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_0370ac00-5c7e-4755-95cc-2ede9fd32e2a" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_5906e244-abf6-4883-9586-9b4ec3d74cee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5906e244-abf6-4883-9586-9b4ec3d74cee_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5906e244-abf6-4883-9586-9b4ec3d74cee" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5906e244-abf6-4883-9586-9b4ec3d74cee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0415a331-d537-48a3-979d-79e9dfe617d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5906e244-abf6-4883-9586-9b4ec3d74cee" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0415a331-d537-48a3-979d-79e9dfe617d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IXYSCorporationMember_81ea336b-7f79-48f0-b0df-fe560c4e1fb2" xlink:href="lfus-20201226.xsd#lfus_IXYSCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0415a331-d537-48a3-979d-79e9dfe617d2" xlink:to="loc_lfus_IXYSCorporationMember_81ea336b-7f79-48f0-b0df-fe560c4e1fb2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_e169d915-963c-46a9-a617-6c8b9102043b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_0370ac00-5c7e-4755-95cc-2ede9fd32e2a" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_e169d915-963c-46a9-a617-6c8b9102043b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_e169d915-963c-46a9-a617-6c8b9102043b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_e169d915-963c-46a9-a617-6c8b9102043b" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_e169d915-963c-46a9-a617-6c8b9102043b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_382dd9a8-4d57-4150-ab79-2520d486b832" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_e169d915-963c-46a9-a617-6c8b9102043b" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_382dd9a8-4d57-4150-ab79-2520d486b832" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCountryMember_6aea3878-3807-4bc6-90ba-65f7c463241d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_382dd9a8-4d57-4150-ab79-2520d486b832" xlink:to="loc_us-gaap_ForeignCountryMember_6aea3878-3807-4bc6-90ba-65f7c463241d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DomesticCountryMember_f6dd90b4-b331-4468-9ad8-80034b841d0f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DomesticCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_382dd9a8-4d57-4150-ab79-2520d486b832" xlink:to="loc_us-gaap_DomesticCountryMember_f6dd90b4-b331-4468-9ad8-80034b841d0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_dfdd2d65-b775-4fa1-a23e-cded9705362e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_0370ac00-5c7e-4755-95cc-2ede9fd32e2a" xlink:to="loc_srt_StatementGeographicalAxis_dfdd2d65-b775-4fa1-a23e-cded9705362e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_dfdd2d65-b775-4fa1-a23e-cded9705362e_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_dfdd2d65-b775-4fa1-a23e-cded9705362e" xlink:to="loc_srt_SegmentGeographicalDomain_dfdd2d65-b775-4fa1-a23e-cded9705362e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_425e8c7f-d4a2-4ac9-a8a6-64f8f8470c38" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_dfdd2d65-b775-4fa1-a23e-cded9705362e" xlink:to="loc_srt_SegmentGeographicalDomain_425e8c7f-d4a2-4ac9-a8a6-64f8f8470c38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CN_6641b2fd-a98a-4c64-be41-f42541d353e7" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_CN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_425e8c7f-d4a2-4ac9-a8a6-64f8f8470c38" xlink:to="loc_country_CN_6641b2fd-a98a-4c64-be41-f42541d353e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityNameAxis_6b493e49-6e62-4a4b-9a50-ca8e6cdc123a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_0370ac00-5c7e-4755-95cc-2ede9fd32e2a" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameAxis_6b493e49-6e62-4a4b-9a50-ca8e6cdc123a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityNameDomain_6b493e49-6e62-4a4b-9a50-ca8e6cdc123a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameAxis_6b493e49-6e62-4a4b-9a50-ca8e6cdc123a" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameDomain_6b493e49-6e62-4a4b-9a50-ca8e6cdc123a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityNameDomain_b1af5387-0f08-4342-93a9-9afb8364850b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameAxis_6b493e49-6e62-4a4b-9a50-ca8e6cdc123a" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameDomain_b1af5387-0f08-4342-93a9-9afb8364850b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CanadaRevenueAgencyMember_10c3e329-40c4-442d-8736-c56c77b03e98" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CanadaRevenueAgencyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameDomain_b1af5387-0f08-4342-93a9-9afb8364850b" xlink:to="loc_us-gaap_CanadaRevenueAgencyMember_10c3e329-40c4-442d-8736-c56c77b03e98" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/IncomeTaxesFederalStateandForeignIncomeTaxBenefitExpenseDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#IncomeTaxesFederalStateandForeignIncomeTaxBenefitExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/IncomeTaxesFederalStateandForeignIncomeTaxBenefitExpenseDetails" xlink:type="extended" id="id2422b024d6f43f499d74a3a299fff20_IncomeTaxesFederalStateandForeignIncomeTaxBenefitExpenseDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/IncomeTaxesEffectiveIncomeTaxReconciliationandProvisionforIncomeTaxesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#IncomeTaxesEffectiveIncomeTaxReconciliationandProvisionforIncomeTaxesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/IncomeTaxesEffectiveIncomeTaxReconciliationandProvisionforIncomeTaxesDetails" xlink:type="extended" id="ibe49b52d3b3445208afa30932b65c54c_IncomeTaxesEffectiveIncomeTaxReconciliationandProvisionforIncomeTaxesDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/IncomeTaxesDeferredTaxAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#IncomeTaxesDeferredTaxAssetsandLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/IncomeTaxesDeferredTaxAssetsandLiabilitiesDetails" xlink:type="extended" id="ia282db4a16594ae8bbd6597cc828435d_IncomeTaxesDeferredTaxAssetsandLiabilitiesDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/IncomeTaxesReconciliationoftheBeginningandEndingAmountofUnrecognizedTaxBenefitsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#IncomeTaxesReconciliationoftheBeginningandEndingAmountofUnrecognizedTaxBenefitsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/IncomeTaxesReconciliationoftheBeginningandEndingAmountofUnrecognizedTaxBenefitsDetails" xlink:type="extended" id="i48d485516fe7462186137dbef3d51854_IncomeTaxesReconciliationoftheBeginningandEndingAmountofUnrecognizedTaxBenefitsDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/EarningsPerShare" xlink:type="simple" xlink:href="lfus-20201226.xsd#EarningsPerShare"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/EarningsPerShare" xlink:type="extended" id="i60dc6239b7654eea838f31b0e93f1d30_EarningsPerShare"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/EarningsPerShareTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#EarningsPerShareTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/EarningsPerShareTables" xlink:type="extended" id="i6502404fd314438eb1ae43fef9c6f797_EarningsPerShareTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/EarningsPerShareComputationofBasicandDilutedEarningsPerShareDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#EarningsPerShareComputationofBasicandDilutedEarningsPerShareDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/EarningsPerShareComputationofBasicandDilutedEarningsPerShareDetails" xlink:type="extended" id="i76f7e0dc9d414a5faae0343b63934994_EarningsPerShareComputationofBasicandDilutedEarningsPerShareDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/EarningsPerShareNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#EarningsPerShareNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/EarningsPerShareNarrativeDetails" xlink:type="extended" id="i5f2fa3ba530c45868ab121916566a3f2_EarningsPerShareNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_7df76509-19be-4327-ad1d-ffd9b5d9658a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_48c318c2-8323-4250-a0fe-a095ab68c20c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_7df76509-19be-4327-ad1d-ffd9b5d9658a" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_48c318c2-8323-4250-a0fe-a095ab68c20c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_5b263a2c-81b3-4266-a62d-0ecb643d7cdb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_7df76509-19be-4327-ad1d-ffd9b5d9658a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_5b263a2c-81b3-4266-a62d-0ecb643d7cdb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConversionOfStockSharesIssued1_7996c1ff-bd55-4511-a53c-639447673dd4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConversionOfStockSharesIssued1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_7df76509-19be-4327-ad1d-ffd9b5d9658a" xlink:to="loc_us-gaap_ConversionOfStockSharesIssued1_7996c1ff-bd55-4511-a53c-639447673dd4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_0b706fb0-b517-4e7e-81ee-f28608fc8a64" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_7df76509-19be-4327-ad1d-ffd9b5d9658a" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_0b706fb0-b517-4e7e-81ee-f28608fc8a64" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_fb35c94f-1a55-406f-86ae-9d4877289d6d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_7df76509-19be-4327-ad1d-ffd9b5d9658a" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_fb35c94f-1a55-406f-86ae-9d4877289d6d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_ce039b75-892f-40ea-a68b-27cbdfbb65c3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_7df76509-19be-4327-ad1d-ffd9b5d9658a" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_ce039b75-892f-40ea-a68b-27cbdfbb65c3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_d2b2c84b-146d-4546-9667-55b7e64cdc73" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_ce039b75-892f-40ea-a68b-27cbdfbb65c3" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_d2b2c84b-146d-4546-9667-55b7e64cdc73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d2b2c84b-146d-4546-9667-55b7e64cdc73_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_d2b2c84b-146d-4546-9667-55b7e64cdc73" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d2b2c84b-146d-4546-9667-55b7e64cdc73_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_702661c0-b155-4cf2-b27f-f10d098fd70b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_d2b2c84b-146d-4546-9667-55b7e64cdc73" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_702661c0-b155-4cf2-b27f-f10d098fd70b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IXYSCorporationMember_f981169d-440a-4597-9fac-ac19f5b7d6b7" xlink:href="lfus-20201226.xsd#lfus_IXYSCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_702661c0-b155-4cf2-b27f-f10d098fd70b" xlink:to="loc_lfus_IXYSCorporationMember_f981169d-440a-4597-9fac-ac19f5b7d6b7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherSignificantNoncashTransactionsByUniqueDescriptionAxis_81cd87f5-587b-4386-8b01-f6c1c958cffc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherSignificantNoncashTransactionsByUniqueDescriptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_ce039b75-892f-40ea-a68b-27cbdfbb65c3" xlink:to="loc_us-gaap_OtherSignificantNoncashTransactionsByUniqueDescriptionAxis_81cd87f5-587b-4386-8b01-f6c1c958cffc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherSignificantNoncashTransactionNameDomain_81cd87f5-587b-4386-8b01-f6c1c958cffc_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherSignificantNoncashTransactionNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherSignificantNoncashTransactionsByUniqueDescriptionAxis_81cd87f5-587b-4386-8b01-f6c1c958cffc" xlink:to="loc_us-gaap_OtherSignificantNoncashTransactionNameDomain_81cd87f5-587b-4386-8b01-f6c1c958cffc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherSignificantNoncashTransactionNameDomain_5db15f81-df6c-4113-a2db-13658130ab70" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherSignificantNoncashTransactionNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherSignificantNoncashTransactionsByUniqueDescriptionAxis_81cd87f5-587b-4386-8b01-f6c1c958cffc" xlink:to="loc_us-gaap_OtherSignificantNoncashTransactionNameDomain_5db15f81-df6c-4113-a2db-13658130ab70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ConversionOfIXYSEquityAwardsIntoLittlefuseEquityAwardsMember_ad56787b-6500-4c09-a19b-45df5fc302bb" xlink:href="lfus-20201226.xsd#lfus_ConversionOfIXYSEquityAwardsIntoLittlefuseEquityAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherSignificantNoncashTransactionNameDomain_5db15f81-df6c-4113-a2db-13658130ab70" xlink:to="loc_lfus_ConversionOfIXYSEquityAwardsIntoLittlefuseEquityAwardsMember_ad56787b-6500-4c09-a19b-45df5fc302bb" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SegmentInformation" xlink:type="simple" xlink:href="lfus-20201226.xsd#SegmentInformation"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SegmentInformation" xlink:type="extended" id="i42ac967e94a04f648438f1b89c1711c2_SegmentInformation"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SegmentInformationTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#SegmentInformationTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SegmentInformationTables" xlink:type="extended" id="i6d3a7d2ef9a74fba873178c32a679be2_SegmentInformationTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SegmentInformationNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#SegmentInformationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SegmentInformationNarrativeDetails" xlink:type="extended" id="iba66b6e1557d47919bbb0c716a468399_SegmentInformationNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfOperatingSegments_38181602-d547-4c1b-a420-16e72e7f8b66" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NumberOfOperatingSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_us-gaap_NumberOfOperatingSegments_38181602-d547-4c1b-a420-16e72e7f8b66" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_07e7d013-09f2-4480-b5ce-f44392feb786" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_07e7d013-09f2-4480-b5ce-f44392feb786" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostsAndAssetImpairmentCharges_256aff6b-7466-42c7-b247-aa8b89f920c8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCostsAndAssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_us-gaap_RestructuringCostsAndAssetImpairmentCharges_256aff6b-7466-42c7-b247-aa8b89f920c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetImpairmentCharges_68c01f00-593f-4c0e-8412-58d38f67216d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_us-gaap_OtherAssetImpairmentCharges_68c01f00-593f-4c0e-8412-58d38f67216d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_587819b3-505e-4b03-a8ac-f8b10da20a55" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_us-gaap_RestructuringCharges_587819b3-505e-4b03-a8ac-f8b10da20a55" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory_afb2a769-fc4b-4e3f-94c8-e93ecdbcbb9e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory_afb2a769-fc4b-4e3f-94c8-e93ecdbcbb9e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_BusinessCombinationAcquisitionRelatedCostsandIntegrationCostsLegalAccountingandOtherExpenses_49831364-b9b6-437e-a03f-44a574ae5c4c" xlink:href="lfus-20201226.xsd#lfus_BusinessCombinationAcquisitionRelatedCostsandIntegrationCostsLegalAccountingandOtherExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_lfus_BusinessCombinationAcquisitionRelatedCostsandIntegrationCostsLegalAccountingandOtherExpenses_49831364-b9b6-437e-a03f-44a574ae5c4c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_BusinessCombinationBacklogAmortizationCosts_bf03ae30-4d51-460e-a7c4-a4939244c399" xlink:href="lfus-20201226.xsd#lfus_BusinessCombinationBacklogAmortizationCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_lfus_BusinessCombinationBacklogAmortizationCosts_bf03ae30-4d51-460e-a7c4-a4939244c399" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_2374b4a5-28cd-400f-bbe3-af9690088a31" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_us-gaap_ShareBasedCompensation_2374b4a5-28cd-400f-bbe3-af9690088a31" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_BusinessCombinationChangeinControlExpense_2fb82c1c-0c14-4298-9745-a3be3fe6803f" xlink:href="lfus-20201226.xsd#lfus_BusinessCombinationChangeinControlExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_lfus_BusinessCombinationChangeinControlExpense_2fb82c1c-0c14-4298-9745-a3be3fe6803f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_2f2be3df-47ae-44d9-abe6-6b9a4e0589b7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_us-gaap_AssetImpairmentCharges_2f2be3df-47ae-44d9-abe6-6b9a4e0589b7" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_9b4c911d-1fdd-4ee8-a46f-55d75620ecf1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_9b4c911d-1fdd-4ee8-a46f-55d75620ecf1" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c7b8d25a-b943-418a-acf6-a049ad17d150" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_f6b996b8-1080-4391-bc13-8e935ea34533" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_f6b996b8-1080-4391-bc13-8e935ea34533" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6b996b8-1080-4391-bc13-8e935ea34533_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_f6b996b8-1080-4391-bc13-8e935ea34533" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6b996b8-1080-4391-bc13-8e935ea34533_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_35f742cf-a7d5-4031-ad64-5281ddde4230" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_f6b996b8-1080-4391-bc13-8e935ea34533" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_35f742cf-a7d5-4031-ad64-5281ddde4230" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IXYSCorporationMember_4cbe7320-c8aa-4e73-8b4c-9c958e6f1bbc" xlink:href="lfus-20201226.xsd#lfus_IXYSCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_35f742cf-a7d5-4031-ad64-5281ddde4230" xlink:to="loc_lfus_IXYSCorporationMember_4cbe7320-c8aa-4e73-8b4c-9c958e6f1bbc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_2a211e41-905f-4a69-a45f-e6790d060ae6" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:to="loc_srt_ConsolidationItemsAxis_2a211e41-905f-4a69-a45f-e6790d060ae6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_2a211e41-905f-4a69-a45f-e6790d060ae6_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_2a211e41-905f-4a69-a45f-e6790d060ae6" xlink:to="loc_srt_ConsolidationItemsDomain_2a211e41-905f-4a69-a45f-e6790d060ae6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_2fc0f468-1d09-497c-b378-48afe74981ae" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_2a211e41-905f-4a69-a45f-e6790d060ae6" xlink:to="loc_srt_ConsolidationItemsDomain_2fc0f468-1d09-497c-b378-48afe74981ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_16f5e1db-64ec-46bb-8a55-d80d28896f27" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_2fc0f468-1d09-497c-b378-48afe74981ae" xlink:to="loc_us-gaap_CorporateNonSegmentMember_16f5e1db-64ec-46bb-8a55-d80d28896f27" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_6770c7e7-4ef1-485b-9e55-3b33df2603e1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_6770c7e7-4ef1-485b-9e55-3b33df2603e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_6770c7e7-4ef1-485b-9e55-3b33df2603e1_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_6770c7e7-4ef1-485b-9e55-3b33df2603e1" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_6770c7e7-4ef1-485b-9e55-3b33df2603e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_2991ffcc-9f71-417b-b4bd-22cdf1f988cc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_6770c7e7-4ef1-485b-9e55-3b33df2603e1" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_2991ffcc-9f71-417b-b4bd-22cdf1f988cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLossMember_be357474-d02a-404a-b4fb-e0451a3b40cb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_2991ffcc-9f71-417b-b4bd-22cdf1f988cc" xlink:to="loc_us-gaap_OperatingIncomeLossMember_be357474-d02a-404a-b4fb-e0451a3b40cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0bff6a87-56bb-4fd6-b6dd-06ad0bf4459a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0bff6a87-56bb-4fd6-b6dd-06ad0bf4459a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_0bff6a87-56bb-4fd6-b6dd-06ad0bf4459a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0bff6a87-56bb-4fd6-b6dd-06ad0bf4459a" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_0bff6a87-56bb-4fd6-b6dd-06ad0bf4459a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_8eb3b32f-a87b-419b-bd7b-27cc16b79004" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0bff6a87-56bb-4fd6-b6dd-06ad0bf4459a" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_8eb3b32f-a87b-419b-bd7b-27cc16b79004" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_29c5c62a-311e-4560-b4c6-9c718b80cf34" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_8eb3b32f-a87b-419b-bd7b-27cc16b79004" xlink:to="loc_us-gaap_SalesRevenueNetMember_29c5c62a-311e-4560-b4c6-9c718b80cf34" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_9a47ac7b-b3be-4bb3-9947-bf88e19baa6f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_9a47ac7b-b3be-4bb3-9947-bf88e19baa6f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_9a47ac7b-b3be-4bb3-9947-bf88e19baa6f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_9a47ac7b-b3be-4bb3-9947-bf88e19baa6f" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_9a47ac7b-b3be-4bb3-9947-bf88e19baa6f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_bd8b1709-2fd5-4580-bb8f-a60cba47eb43" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_9a47ac7b-b3be-4bb3-9947-bf88e19baa6f" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_bd8b1709-2fd5-4580-bb8f-a60cba47eb43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeographicConcentrationRiskMember_b10c03f8-58e1-4e00-ac93-47ce56433f52" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeographicConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_bd8b1709-2fd5-4580-bb8f-a60cba47eb43" xlink:to="loc_us-gaap_GeographicConcentrationRiskMember_b10c03f8-58e1-4e00-ac93-47ce56433f52" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_244ced59-b8e9-46bc-aeb5-ba9dbc7700ba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_bd8b1709-2fd5-4580-bb8f-a60cba47eb43" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_244ced59-b8e9-46bc-aeb5-ba9dbc7700ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_3886913a-f169-4663-8e73-a0aa9c84e44a" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:to="loc_srt_StatementGeographicalAxis_3886913a-f169-4663-8e73-a0aa9c84e44a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_3886913a-f169-4663-8e73-a0aa9c84e44a_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_3886913a-f169-4663-8e73-a0aa9c84e44a" xlink:to="loc_srt_SegmentGeographicalDomain_3886913a-f169-4663-8e73-a0aa9c84e44a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_eae8405f-5eb4-4954-a00e-6e09ecbc78f3" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_3886913a-f169-4663-8e73-a0aa9c84e44a" xlink:to="loc_srt_SegmentGeographicalDomain_eae8405f-5eb4-4954-a00e-6e09ecbc78f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_7c679ae0-8b9c-47a9-a546-34473b098f49" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_eae8405f-5eb4-4954-a00e-6e09ecbc78f3" xlink:to="loc_us-gaap_NonUsMember_7c679ae0-8b9c-47a9-a546-34473b098f49" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CN_5a1f6a79-c9b7-4794-b6a4-24a154986286" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_CN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_eae8405f-5eb4-4954-a00e-6e09ecbc78f3" xlink:to="loc_country_CN_5a1f6a79-c9b7-4794-b6a4-24a154986286" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_c27d270b-e3f4-47fa-ab38-8e01bcce4602" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:to="loc_srt_MajorCustomersAxis_c27d270b-e3f4-47fa-ab38-8e01bcce4602" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_c27d270b-e3f4-47fa-ab38-8e01bcce4602_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_c27d270b-e3f4-47fa-ab38-8e01bcce4602" xlink:to="loc_srt_NameOfMajorCustomerDomain_c27d270b-e3f4-47fa-ab38-8e01bcce4602_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_7db94a02-ede7-4a07-9c84-ec5dbf0a90ad" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_c27d270b-e3f4-47fa-ab38-8e01bcce4602" xlink:to="loc_srt_NameOfMajorCustomerDomain_7db94a02-ede7-4a07-9c84-ec5dbf0a90ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ArrowElectronicsIncMember_8868d2ea-39d2-4ec1-9239-e8fdd060f131" xlink:href="lfus-20201226.xsd#lfus_ArrowElectronicsIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_7db94a02-ede7-4a07-9c84-ec5dbf0a90ad" xlink:to="loc_lfus_ArrowElectronicsIncMember_8868d2ea-39d2-4ec1-9239-e8fdd060f131" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_039ed51f-bd9d-4ef0-a8d4-6f60882e85eb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_039ed51f-bd9d-4ef0-a8d4-6f60882e85eb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_039ed51f-bd9d-4ef0-a8d4-6f60882e85eb_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_039ed51f-bd9d-4ef0-a8d4-6f60882e85eb" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_039ed51f-bd9d-4ef0-a8d4-6f60882e85eb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_a2641fdb-5142-4d71-b9f3-8751cf1b69ba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_039ed51f-bd9d-4ef0-a8d4-6f60882e85eb" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_a2641fdb-5142-4d71-b9f3-8751cf1b69ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherRestructuringMember_447ad91f-370b-4cc2-a6dc-a2336527eee5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherRestructuringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_a2641fdb-5142-4d71-b9f3-8751cf1b69ba" xlink:to="loc_us-gaap_OtherRestructuringMember_447ad91f-370b-4cc2-a6dc-a2336527eee5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_4948f310-cb5e-4470-9948-321c3d900076" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_a2641fdb-5142-4d71-b9f3-8751cf1b69ba" xlink:to="loc_us-gaap_EmployeeSeveranceMember_4948f310-cb5e-4470-9948-321c3d900076" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_af4d6667-22ae-477a-ac4d-9ab00314650c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0fed2b51-c4c1-43ab-a8c1-0cf0f554cd01" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_af4d6667-22ae-477a-ac4d-9ab00314650c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_af4d6667-22ae-477a-ac4d-9ab00314650c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_af4d6667-22ae-477a-ac4d-9ab00314650c" xlink:to="loc_us-gaap_SegmentDomain_af4d6667-22ae-477a-ac4d-9ab00314650c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_612d042b-fc9a-4915-85ea-99049b320d30" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_af4d6667-22ae-477a-ac4d-9ab00314650c" xlink:to="loc_us-gaap_SegmentDomain_612d042b-fc9a-4915-85ea-99049b320d30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AutomotiveMember_3b119d3e-68f0-4dfa-96aa-e7d18982aa63" xlink:href="lfus-20201226.xsd#lfus_AutomotiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_612d042b-fc9a-4915-85ea-99049b320d30" xlink:to="loc_lfus_AutomotiveMember_3b119d3e-68f0-4dfa-96aa-e7d18982aa63" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SegmentInformationDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#SegmentInformationDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SegmentInformationDetails" xlink:type="extended" id="i0ca718a8792a426ab607e30019c211e3_SegmentInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_94c14cfb-89fd-4518-bb43-49313bdb5ec0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_b8148b38-8b73-41e9-8500-0341aee01406" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_94c14cfb-89fd-4518-bb43-49313bdb5ec0" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_b8148b38-8b73-41e9-8500-0341aee01406" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_48437e45-a1b0-4a19-9a00-d13ff31fe51a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_94c14cfb-89fd-4518-bb43-49313bdb5ec0" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_48437e45-a1b0-4a19-9a00-d13ff31fe51a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_b7446a5b-a25c-4cf4-a1ef-8f0103fd7058" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_94c14cfb-89fd-4518-bb43-49313bdb5ec0" xlink:to="loc_us-gaap_OperatingIncomeLoss_b7446a5b-a25c-4cf4-a1ef-8f0103fd7058" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_0d7e8efd-6651-4b69-9b21-c3471355b9c3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_94c14cfb-89fd-4518-bb43-49313bdb5ec0" xlink:to="loc_us-gaap_InterestExpense_0d7e8efd-6651-4b69-9b21-c3471355b9c3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_f932a375-fdea-47c5-9efd-6c15d5fb359b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_94c14cfb-89fd-4518-bb43-49313bdb5ec0" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_f932a375-fdea-47c5-9efd-6c15d5fb359b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_0c76ad46-fd60-4c93-b8a7-79ce80bb1621" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_94c14cfb-89fd-4518-bb43-49313bdb5ec0" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_0c76ad46-fd60-4c93-b8a7-79ce80bb1621" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_a2ff3081-560e-4fd1-8545-8cca279bd89d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_94c14cfb-89fd-4518-bb43-49313bdb5ec0" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_a2ff3081-560e-4fd1-8545-8cca279bd89d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_2b4047b6-3503-47a7-a506-abd40b99c1fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_94c14cfb-89fd-4518-bb43-49313bdb5ec0" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_2b4047b6-3503-47a7-a506-abd40b99c1fe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_94d49b93-7c6c-4a87-b009-bc8548fe40b6" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_2b4047b6-3503-47a7-a506-abd40b99c1fe" xlink:to="loc_srt_ConsolidationItemsAxis_94d49b93-7c6c-4a87-b009-bc8548fe40b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_94d49b93-7c6c-4a87-b009-bc8548fe40b6_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_94d49b93-7c6c-4a87-b009-bc8548fe40b6" xlink:to="loc_srt_ConsolidationItemsDomain_94d49b93-7c6c-4a87-b009-bc8548fe40b6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_71d4dea0-4d40-4ad2-8bf7-2c91150527ab" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_94d49b93-7c6c-4a87-b009-bc8548fe40b6" xlink:to="loc_srt_ConsolidationItemsDomain_71d4dea0-4d40-4ad2-8bf7-2c91150527ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_cce279ba-be49-400c-9783-780c2ac394e7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_71d4dea0-4d40-4ad2-8bf7-2c91150527ab" xlink:to="loc_us-gaap_OperatingSegmentsMember_cce279ba-be49-400c-9783-780c2ac394e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_15724249-cf76-450d-a0d6-accbe88fe6eb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_71d4dea0-4d40-4ad2-8bf7-2c91150527ab" xlink:to="loc_us-gaap_CorporateNonSegmentMember_15724249-cf76-450d-a0d6-accbe88fe6eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_92bf7356-4394-4640-8fd0-86e3f4e23fe3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_2b4047b6-3503-47a7-a506-abd40b99c1fe" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_92bf7356-4394-4640-8fd0-86e3f4e23fe3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_92bf7356-4394-4640-8fd0-86e3f4e23fe3_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_92bf7356-4394-4640-8fd0-86e3f4e23fe3" xlink:to="loc_us-gaap_SegmentDomain_92bf7356-4394-4640-8fd0-86e3f4e23fe3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_fda35e10-f69c-49b0-aab6-1fbe9731591e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_92bf7356-4394-4640-8fd0-86e3f4e23fe3" xlink:to="loc_us-gaap_SegmentDomain_fda35e10-f69c-49b0-aab6-1fbe9731591e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ElectronicsMember_8fb366f0-8d8f-45d1-b06f-13119de65163" xlink:href="lfus-20201226.xsd#lfus_ElectronicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fda35e10-f69c-49b0-aab6-1fbe9731591e" xlink:to="loc_lfus_ElectronicsMember_8fb366f0-8d8f-45d1-b06f-13119de65163" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AutomotiveMember_8c696f59-81b8-4091-b741-8e3e10f8c66f" xlink:href="lfus-20201226.xsd#lfus_AutomotiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fda35e10-f69c-49b0-aab6-1fbe9731591e" xlink:to="loc_lfus_AutomotiveMember_8c696f59-81b8-4091-b741-8e3e10f8c66f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_IndustrialMember_9dfd598f-7e91-4050-878f-bb2008c52aa7" xlink:href="lfus-20201226.xsd#lfus_IndustrialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fda35e10-f69c-49b0-aab6-1fbe9731591e" xlink:to="loc_lfus_IndustrialMember_9dfd598f-7e91-4050-878f-bb2008c52aa7" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SegmentInformationRevenuesandLonglivedAssetsbyGeographicalAreaDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#SegmentInformationRevenuesandLonglivedAssetsbyGeographicalAreaDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SegmentInformationRevenuesandLonglivedAssetsbyGeographicalAreaDetails" xlink:type="extended" id="ie8f9dd015f964c7b8bc9040ebd2caa1f_SegmentInformationRevenuesandLonglivedAssetsbyGeographicalAreaDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_3f322bad-80fa-457f-b530-37c75270895a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_2560f346-da89-4672-a5c3-8aaf062fae79" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3f322bad-80fa-457f-b530-37c75270895a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_2560f346-da89-4672-a5c3-8aaf062fae79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncurrentAssets_a1afb151-0d83-4097-b804-df166f591ab9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3f322bad-80fa-457f-b530-37c75270895a" xlink:to="loc_us-gaap_NoncurrentAssets_a1afb151-0d83-4097-b804-df166f591ab9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAdditions_7c735290-fd63-4633-9c74-72a57b7c76a6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3f322bad-80fa-457f-b530-37c75270895a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAdditions_7c735290-fd63-4633-9c74-72a57b7c76a6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_82ac2891-f939-4b84-ad50-2685dc682fd3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3f322bad-80fa-457f-b530-37c75270895a" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_82ac2891-f939-4b84-ad50-2685dc682fd3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_741d5111-8a58-46a1-8553-7a8d40084cf7" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_82ac2891-f939-4b84-ad50-2685dc682fd3" xlink:to="loc_srt_StatementGeographicalAxis_741d5111-8a58-46a1-8553-7a8d40084cf7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_741d5111-8a58-46a1-8553-7a8d40084cf7_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_741d5111-8a58-46a1-8553-7a8d40084cf7" xlink:to="loc_srt_SegmentGeographicalDomain_741d5111-8a58-46a1-8553-7a8d40084cf7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_85705d7d-5bb0-4dc1-892f-ae5473733740" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_741d5111-8a58-46a1-8553-7a8d40084cf7" xlink:to="loc_srt_SegmentGeographicalDomain_85705d7d-5bb0-4dc1-892f-ae5473733740" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_074a1a20-76d3-4bc3-bbcc-9399271c146d" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_85705d7d-5bb0-4dc1-892f-ae5473733740" xlink:to="loc_country_US_074a1a20-76d3-4bc3-bbcc-9399271c146d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CN_019a2756-7fb4-4d98-84a4-0b8ba99d0123" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_CN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_85705d7d-5bb0-4dc1-892f-ae5473733740" xlink:to="loc_country_CN_019a2756-7fb4-4d98-84a4-0b8ba99d0123" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_2f6150c0-bf6c-4f1b-9555-16ebd0e29923" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_85705d7d-5bb0-4dc1-892f-ae5473733740" xlink:to="loc_country_MX_2f6150c0-bf6c-4f1b-9555-16ebd0e29923" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_DE_14b2a6fa-ea97-4ded-82b2-9a160ed96680" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_DE"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_85705d7d-5bb0-4dc1-892f-ae5473733740" xlink:to="loc_country_DE_14b2a6fa-ea97-4ded-82b2-9a160ed96680" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_PH_42ae496b-cb8f-4f11-9632-12ae11f1c3f7" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_PH"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_85705d7d-5bb0-4dc1-892f-ae5473733740" xlink:to="loc_country_PH_42ae496b-cb8f-4f11-9632-12ae11f1c3f7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_OtherCountriesMember_3a929aa1-af5d-49e0-9fc9-e9372dd56402" xlink:href="lfus-20201226.xsd#lfus_OtherCountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_85705d7d-5bb0-4dc1-892f-ae5473733740" xlink:to="loc_lfus_OtherCountriesMember_3a929aa1-af5d-49e0-9fc9-e9372dd56402" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SelectedQuarterlyFinancialDataUnaudited" xlink:type="simple" xlink:href="lfus-20201226.xsd#SelectedQuarterlyFinancialDataUnaudited"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SelectedQuarterlyFinancialDataUnaudited" xlink:type="extended" id="ia658cc01782d48428290f854e05e05ed_SelectedQuarterlyFinancialDataUnaudited"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SelectedQuarterlyFinancialDataUnauditedTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#SelectedQuarterlyFinancialDataUnauditedTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SelectedQuarterlyFinancialDataUnauditedTables" xlink:type="extended" id="id68681c7efbd4815a8844a6e9652f314_SelectedQuarterlyFinancialDataUnauditedTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SelectedQuarterlyFinancialDataUnauditedQuarterlyFinancialInformationDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#SelectedQuarterlyFinancialDataUnauditedQuarterlyFinancialInformationDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SelectedQuarterlyFinancialDataUnauditedQuarterlyFinancialInformationDetails" xlink:type="extended" id="id0eba122b5cd494b89a4758b6f9a3cb9_SelectedQuarterlyFinancialDataUnauditedQuarterlyFinancialInformationDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SelectedQuarterlyFinancialDataNarrativeDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#SelectedQuarterlyFinancialDataNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SelectedQuarterlyFinancialDataNarrativeDetails" xlink:type="extended" id="ifc712b98e6aa42bba509907f3e3e3219_SelectedQuarterlyFinancialDataNarrativeDetails"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/RelatedPartyTransactions" xlink:type="simple" xlink:href="lfus-20201226.xsd#RelatedPartyTransactions"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/RelatedPartyTransactions" xlink:type="extended" id="icb62e52e3acc4bed80d9b4b6903d4e98_RelatedPartyTransactions"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/RelatedPartyDisclosuresTables" xlink:type="simple" xlink:href="lfus-20201226.xsd#RelatedPartyDisclosuresTables"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/RelatedPartyDisclosuresTables" xlink:type="extended" id="ib3597ab5b82049988a01bebbcf3b0334_RelatedPartyDisclosuresTables"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/RelatedPartyTransactionsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#RelatedPartyTransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/RelatedPartyTransactionsDetails" xlink:type="extended" id="i55e342f79068469cb44fcbfbf941c8bc_RelatedPartyTransactionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_e037898f-8145-4b56-b5ef-68dfd2fcca5e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_f15ae8f7-ce0e-49f1-87c5-9f99b90fb265" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_e037898f-8145-4b56-b5ef-68dfd2fcca5e" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_f15ae8f7-ce0e-49f1-87c5-9f99b90fb265" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromRelatedParties_c822d83f-dc67-4fa3-9069-bf09586488ad" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromRelatedParties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_e037898f-8145-4b56-b5ef-68dfd2fcca5e" xlink:to="loc_us-gaap_RevenueFromRelatedParties_c822d83f-dc67-4fa3-9069-bf09586488ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty_7bebde6b-0e70-4177-b60f-ed9f67f37ab5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_e037898f-8145-4b56-b5ef-68dfd2fcca5e" xlink:to="loc_us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty_7bebde6b-0e70-4177-b60f-ed9f67f37ab5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableRelatedParties_4e814bc5-110d-48f9-ad8a-933cfe98f86d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsReceivableRelatedParties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_e037898f-8145-4b56-b5ef-68dfd2fcca5e" xlink:to="loc_us-gaap_AccountsReceivableRelatedParties_4e814bc5-110d-48f9-ad8a-933cfe98f86d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent_d6e9dc9a-4235-4bc2-af85-ae1839ab0f03" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_e037898f-8145-4b56-b5ef-68dfd2fcca5e" xlink:to="loc_us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent_d6e9dc9a-4235-4bc2-af85-ae1839ab0f03" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Investments_b96b9e3b-40da-422b-818c-948671ee231d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Investments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_e037898f-8145-4b56-b5ef-68dfd2fcca5e" xlink:to="loc_us-gaap_Investments_b96b9e3b-40da-422b-818c-948671ee231d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_d76829d4-c0b5-4602-b446-5ba66088e4dc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_e037898f-8145-4b56-b5ef-68dfd2fcca5e" xlink:to="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_d76829d4-c0b5-4602-b446-5ba66088e4dc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8da99475-2300-471c-998b-082ccc682918" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_e037898f-8145-4b56-b5ef-68dfd2fcca5e" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8da99475-2300-471c-998b-082ccc682918" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2893c359-2e48-4205-94db-5f42e1b64ebe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8da99475-2300-471c-998b-082ccc682918" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2893c359-2e48-4205-94db-5f42e1b64ebe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_2893c359-2e48-4205-94db-5f42e1b64ebe_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2893c359-2e48-4205-94db-5f42e1b64ebe" xlink:to="loc_us-gaap_RelatedPartyDomain_2893c359-2e48-4205-94db-5f42e1b64ebe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_592f1aa9-79ab-4a3f-ab10-e924e939ef69" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2893c359-2e48-4205-94db-5f42e1b64ebe" xlink:to="loc_us-gaap_RelatedPartyDomain_592f1aa9-79ab-4a3f-ab10-e924e939ef69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_45855928-743d-4db2-9694-4ffe035c7ea5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvesteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_592f1aa9-79ab-4a3f-ab10-e924e939ef69" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_45855928-743d-4db2-9694-4ffe035c7ea5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_18de013d-27c9-4f38-8e0f-cc03543a18ab" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8da99475-2300-471c-998b-082ccc682918" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_18de013d-27c9-4f38-8e0f-cc03543a18ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_18de013d-27c9-4f38-8e0f-cc03543a18ab_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_18de013d-27c9-4f38-8e0f-cc03543a18ab" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_18de013d-27c9-4f38-8e0f-cc03543a18ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_b0453283-48d2-4832-93b5-8f2daf17bbcb" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_18de013d-27c9-4f38-8e0f-cc03543a18ab" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_b0453283-48d2-4832-93b5-8f2daf17bbcb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_PowersemMember_77167b6c-4397-4a1e-954a-0b49f47d1e91" xlink:href="lfus-20201226.xsd#lfus_PowersemMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b0453283-48d2-4832-93b5-8f2daf17bbcb" xlink:to="loc_lfus_PowersemMember_77167b6c-4397-4a1e-954a-0b49f47d1e91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_EBTechMember_d49c624e-4c36-407b-85b9-318f733a7a0e" xlink:href="lfus-20201226.xsd#lfus_EBTechMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b0453283-48d2-4832-93b5-8f2daf17bbcb" xlink:to="loc_lfus_EBTechMember_d49c624e-4c36-407b-85b9-318f733a7a0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ATECMember_de214e32-940c-4ec7-8847-c20fc100ada1" xlink:href="lfus-20201226.xsd#lfus_ATECMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b0453283-48d2-4832-93b5-8f2daf17bbcb" xlink:to="loc_lfus_ATECMember_de214e32-940c-4ec7-8847-c20fc100ada1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_VTOOLLtdAndSecurepushLtdMember_7a2c4c9a-8b7d-4247-a279-5bd314b7ff4d" xlink:href="lfus-20201226.xsd#lfus_VTOOLLtdAndSecurepushLtdMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b0453283-48d2-4832-93b5-8f2daf17bbcb" xlink:to="loc_lfus_VTOOLLtdAndSecurepushLtdMember_7a2c4c9a-8b7d-4247-a279-5bd314b7ff4d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_32e5cd19-25c5-4351-b77a-b06098355004" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8da99475-2300-471c-998b-082ccc682918" xlink:to="loc_srt_CounterpartyNameAxis_32e5cd19-25c5-4351-b77a-b06098355004" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_32e5cd19-25c5-4351-b77a-b06098355004_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_32e5cd19-25c5-4351-b77a-b06098355004" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_32e5cd19-25c5-4351-b77a-b06098355004_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cfb8898a-b3bf-44e3-846f-4129e9bed5d2" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_32e5cd19-25c5-4351-b77a-b06098355004" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cfb8898a-b3bf-44e3-846f-4129e9bed5d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_PowersemMember_da2648f5-a0a3-4c00-b816-2022485cfc45" xlink:href="lfus-20201226.xsd#lfus_PowersemMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cfb8898a-b3bf-44e3-846f-4129e9bed5d2" xlink:to="loc_lfus_PowersemMember_da2648f5-a0a3-4c00-b816-2022485cfc45" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_EBTechMember_70af9138-9ece-46ed-81f4-ed2b136f9666" xlink:href="lfus-20201226.xsd#lfus_EBTechMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cfb8898a-b3bf-44e3-846f-4129e9bed5d2" xlink:to="loc_lfus_EBTechMember_70af9138-9ece-46ed-81f4-ed2b136f9666" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_ATECMember_3224619b-bf57-44c7-8d75-241c50ff5d15" xlink:href="lfus-20201226.xsd#lfus_ATECMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cfb8898a-b3bf-44e3-846f-4129e9bed5d2" xlink:to="loc_lfus_ATECMember_3224619b-bf57-44c7-8d75-241c50ff5d15" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SubsequentEvents" xlink:type="simple" xlink:href="lfus-20201226.xsd#SubsequentEvents"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SubsequentEvents" xlink:type="extended" id="i2c9f660eb34a4aada38f14ec9dbb75d0_SubsequentEvents"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/SubsequentEventsDetails" xlink:type="extended" id="i4c153e09a1df4c0fa5851fd9e301c7e3_SubsequentEventsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_306025e5-2585-4fa8-af2e-1e42808a9e3f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_AnnualizedSales_8d86c733-ca77-429f-a77d-7f2cbd31d718" xlink:href="lfus-20201226.xsd#lfus_AnnualizedSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_306025e5-2585-4fa8-af2e-1e42808a9e3f" xlink:to="loc_lfus_AnnualizedSales_8d86c733-ca77-429f-a77d-7f2cbd31d718" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAcquiredFromAcquisition_bd9c3dce-9604-4227-9062-2ca3e84da668" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAcquiredFromAcquisition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_306025e5-2585-4fa8-af2e-1e42808a9e3f" xlink:to="loc_us-gaap_CashAcquiredFromAcquisition_bd9c3dce-9604-4227-9062-2ca3e84da668" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_0dbfa4be-f110-44c8-bb46-ad1d5ebcd1e2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_306025e5-2585-4fa8-af2e-1e42808a9e3f" xlink:to="loc_us-gaap_SubsequentEventTable_0dbfa4be-f110-44c8-bb46-ad1d5ebcd1e2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_425c34f9-a0f6-4d09-8b1a-38a475884181" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_0dbfa4be-f110-44c8-bb46-ad1d5ebcd1e2" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_425c34f9-a0f6-4d09-8b1a-38a475884181" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_425c34f9-a0f6-4d09-8b1a-38a475884181_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_425c34f9-a0f6-4d09-8b1a-38a475884181" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_425c34f9-a0f6-4d09-8b1a-38a475884181_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_eba7c53f-1970-4a29-9d07-6e8b316fc4df" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_425c34f9-a0f6-4d09-8b1a-38a475884181" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_eba7c53f-1970-4a29-9d07-6e8b316fc4df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_3511e5e4-eb9c-460a-b0c3-2800b851f29f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_eba7c53f-1970-4a29-9d07-6e8b316fc4df" xlink:to="loc_us-gaap_SubsequentEventMember_3511e5e4-eb9c-460a-b0c3-2800b851f29f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_b15fe14b-b023-4588-b151-22b3e401abd6" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_0dbfa4be-f110-44c8-bb46-ad1d5ebcd1e2" xlink:to="loc_dei_LegalEntityAxis_b15fe14b-b023-4588-b151-22b3e401abd6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_b15fe14b-b023-4588-b151-22b3e401abd6_default" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_b15fe14b-b023-4588-b151-22b3e401abd6" xlink:to="loc_dei_EntityDomain_b15fe14b-b023-4588-b151-22b3e401abd6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_c5042257-d2cc-46c7-bf9a-c9bec7b4f9e2" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_b15fe14b-b023-4588-b151-22b3e401abd6" xlink:to="loc_dei_EntityDomain_c5042257-d2cc-46c7-bf9a-c9bec7b4f9e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_HartlandControlsMember_7083f319-9e27-436f-9b2c-755248988768" xlink:href="lfus-20201226.xsd#lfus_HartlandControlsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_c5042257-d2cc-46c7-bf9a-c9bec7b4f9e2" xlink:to="loc_lfus_HartlandControlsMember_7083f319-9e27-436f-9b2c-755248988768" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_488c095e-f181-4900-982c-2e64feb24580" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_0dbfa4be-f110-44c8-bb46-ad1d5ebcd1e2" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_488c095e-f181-4900-982c-2e64feb24580" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_488c095e-f181-4900-982c-2e64feb24580_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_488c095e-f181-4900-982c-2e64feb24580" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_488c095e-f181-4900-982c-2e64feb24580_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9580d7fb-9dbe-4836-8a96-e40a44940ba2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_488c095e-f181-4900-982c-2e64feb24580" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9580d7fb-9dbe-4836-8a96-e40a44940ba2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_HartlandControlsMember_d0fe6ab5-dcc1-4b3e-9e1c-988128892ef5" xlink:href="lfus-20201226.xsd#lfus_HartlandControlsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9580d7fb-9dbe-4836-8a96-e40a44940ba2" xlink:to="loc_lfus_HartlandControlsMember_d0fe6ab5-dcc1-4b3e-9e1c-988128892ef5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.littelfuse.com/role/ScheduleIIValuationandQualifyingAccountsandReserves" xlink:type="simple" xlink:href="lfus-20201226.xsd#ScheduleIIValuationandQualifyingAccountsandReserves"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/ScheduleIIValuationandQualifyingAccountsandReserves" xlink:type="extended" id="i2de5b8d5124343a0aef15246e331eb94_ScheduleIIValuationandQualifyingAccountsandReserves"/>
  <link:roleRef roleURI="http://www.littelfuse.com/role/ScheduleIIValuationandQualifyingAccountsandReservesDetails" xlink:type="simple" xlink:href="lfus-20201226.xsd#ScheduleIIValuationandQualifyingAccountsandReservesDetails"/>
  <link:definitionLink xlink:role="http://www.littelfuse.com/role/ScheduleIIValuationandQualifyingAccountsandReservesDetails" xlink:type="extended" id="i5b7cb83b2399497cb88c5c6dae47a534_ScheduleIIValuationandQualifyingAccountsandReservesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_5ffe12a8-448e-4de9-9750-86490c20a7ca" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ValuationAndQualifyingAccountsDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_38f2f343-d998-4b62-a94d-d10f16caf0f0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MovementInValuationAllowancesAndReservesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_5ffe12a8-448e-4de9-9750-86490c20a7ca" xlink:to="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_38f2f343-d998-4b62-a94d-d10f16caf0f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_0b742cbc-3f55-404a-b0eb-318add8c466a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_38f2f343-d998-4b62-a94d-d10f16caf0f0" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesBalance_0b742cbc-3f55-404a-b0eb-318add8c466a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense_14ecdba9-f1f2-4e23-a8a7-2472e4c780e3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_38f2f343-d998-4b62-a94d-d10f16caf0f0" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense_14ecdba9-f1f2-4e23-a8a7-2472e4c780e3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDeductions_3deebee8-2446-42aa-a5f6-3d8c357c120f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDeductions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_38f2f343-d998-4b62-a94d-d10f16caf0f0" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDeductions_3deebee8-2446-42aa-a5f6-3d8c357c120f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesAdjustments_2417a234-a3b6-4599-86c3-fb09ca515f9e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_38f2f343-d998-4b62-a94d-d10f16caf0f0" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesAdjustments_2417a234-a3b6-4599-86c3-fb09ca515f9e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_d7603f75-b981-42f5-a97b-3c9e757e629d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_a09cd470-540f-4845-92c6-6cbe88dfff4e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ValuationAndQualifyingAccountsDisclosureTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_5ffe12a8-448e-4de9-9750-86490c20a7ca" xlink:to="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_a09cd470-540f-4845-92c6-6cbe88dfff4e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_249898f9-abc6-40e7-8b1f-e858cbd596f5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_a09cd470-540f-4845-92c6-6cbe88dfff4e" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_249898f9-abc6-40e7-8b1f-e858cbd596f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_249898f9-abc6-40e7-8b1f-e858cbd596f5_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_249898f9-abc6-40e7-8b1f-e858cbd596f5" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_249898f9-abc6-40e7-8b1f-e858cbd596f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_ac76f6cb-9606-447d-b3d4-a740d7dfa342" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_249898f9-abc6-40e7-8b1f-e858cbd596f5" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_ac76f6cb-9606-447d-b3d4-a740d7dfa342" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForCreditLossMember_c88fa27a-18c8-4da0-8ec6-eb53a6bbe38b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllowanceForCreditLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_ac76f6cb-9606-447d-b3d4-a740d7dfa342" xlink:to="loc_us-gaap_AllowanceForCreditLossMember_c88fa27a-18c8-4da0-8ec6-eb53a6bbe38b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_lfus_SECSchedule1209ReserveSalesDiscountsandAllowancesMember_2ff6342f-8642-45c6-a370-809c33e28ef7" xlink:href="lfus-20201226.xsd#lfus_SECSchedule1209ReserveSalesDiscountsandAllowancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_ac76f6cb-9606-447d-b3d4-a740d7dfa342" xlink:to="loc_lfus_SECSchedule1209ReserveSalesDiscountsandAllowancesMember_2ff6342f-8642-45c6-a370-809c33e28ef7" xlink:type="arc" order="1"/>
  </link:definitionLink>
</link:linkbase>
