<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <roleRef roleURI="http://www.qualys.com/role/CommitmentsAndContingencies" xlink:href="qlys-20150630.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CommitmentsAndContingenciesLeaseNarrativeDetails" xlink:href="qlys-20150630.xsd#CommitmentsAndContingenciesLeaseNarrativeDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CommitmentsAndContingenciesSalesAndOtherTaxesDetails" xlink:href="qlys-20150630.xsd#CommitmentsAndContingenciesSalesAndOtherTaxesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CommitmentsAndContingenciesScheduleOfLeasesDetails" xlink:href="qlys-20150630.xsd#CommitmentsAndContingenciesScheduleOfLeasesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CommitmentsAndContingenciesTables" xlink:href="qlys-20150630.xsd#CommitmentsAndContingenciesTables" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CompanyAndSummaryOfSignificantAccountingPolicies" xlink:href="qlys-20150630.xsd#CompanyAndSummaryOfSignificantAccountingPolicies" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CompanyAndSummaryOfSignificantAccountingPoliciesCorrectionOfImmaterialErrorDetails" xlink:href="qlys-20150630.xsd#CompanyAndSummaryOfSignificantAccountingPoliciesCorrectionOfImmaterialErrorDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CompanyAndSummaryOfSignificantAccountingPoliciesDetails" xlink:href="qlys-20150630.xsd#CompanyAndSummaryOfSignificantAccountingPoliciesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CompanyAndSummaryOfSignificantAccountingPoliciesPolicies" xlink:href="qlys-20150630.xsd#CompanyAndSummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CompanyAndSummaryOfSignificantAccountingPoliciesTables" xlink:href="qlys-20150630.xsd#CompanyAndSummaryOfSignificantAccountingPoliciesTables" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CondensedConsolidatedBalanceSheets" xlink:href="qlys-20150630.xsd#CondensedConsolidatedBalanceSheets" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CondensedConsolidatedBalanceSheetsParenthetical" xlink:href="qlys-20150630.xsd#CondensedConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CondensedConsolidatedStatementsOfCashFlows" xlink:href="qlys-20150630.xsd#CondensedConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CondensedConsolidatedStatementsOfComprehensiveIncome" xlink:href="qlys-20150630.xsd#CondensedConsolidatedStatementsOfComprehensiveIncome" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/CondensedConsolidatedStatementsOfOperations" xlink:href="qlys-20150630.xsd#CondensedConsolidatedStatementsOfOperations" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/DocumentAndEntityInformation" xlink:href="qlys-20150630.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/FairValueOfFinancialInstruments" xlink:href="qlys-20150630.xsd#FairValueOfFinancialInstruments" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/FairValueOfFinancialInstrumentsCashAndCashEquivalentsAvailableForSaleSecuritiesReconciliationDetails" xlink:href="qlys-20150630.xsd#FairValueOfFinancialInstrumentsCashAndCashEquivalentsAvailableForSaleSecuritiesReconciliationDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/FairValueOfFinancialInstrumentsContractualMaturityDetails" xlink:href="qlys-20150630.xsd#FairValueOfFinancialInstrumentsContractualMaturityDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/FairValueOfFinancialInstrumentsDerivativesDetails" xlink:href="qlys-20150630.xsd#FairValueOfFinancialInstrumentsDerivativesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/FairValueOfFinancialInstrumentsFairValueHierarchyDetails" xlink:href="qlys-20150630.xsd#FairValueOfFinancialInstrumentsFairValueHierarchyDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/FairValueOfFinancialInstrumentsTables" xlink:href="qlys-20150630.xsd#FairValueOfFinancialInstrumentsTables" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/GoodwillAndIntangibleAssetsNet" xlink:href="qlys-20150630.xsd#GoodwillAndIntangibleAssetsNet" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/GoodwillAndIntangibleAssetsNetDetails" xlink:href="qlys-20150630.xsd#GoodwillAndIntangibleAssetsNetDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/GoodwillAndIntangibleAssetsNetFutureAmortizationDetails" xlink:href="qlys-20150630.xsd#GoodwillAndIntangibleAssetsNetFutureAmortizationDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/GoodwillAndIntangibleAssetsNetTables" xlink:href="qlys-20150630.xsd#GoodwillAndIntangibleAssetsNetTables" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/IncomeTaxes" xlink:href="qlys-20150630.xsd#IncomeTaxes" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/IncomeTaxesDetails" xlink:href="qlys-20150630.xsd#IncomeTaxesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/NetIncomePerShare" xlink:href="qlys-20150630.xsd#NetIncomePerShare" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/NetIncomePerShareDetails" xlink:href="qlys-20150630.xsd#NetIncomePerShareDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/NetIncomePerShareTables" xlink:href="qlys-20150630.xsd#NetIncomePerShareTables" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/OtherIncomeExpenseNet" xlink:href="qlys-20150630.xsd#OtherIncomeExpenseNet" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/OtherIncomeExpenseNetDetails" xlink:href="qlys-20150630.xsd#OtherIncomeExpenseNetDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/OtherIncomeExpenseNetTables" xlink:href="qlys-20150630.xsd#OtherIncomeExpenseNetTables" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/PropertyAndEquipmentNet" xlink:href="qlys-20150630.xsd#PropertyAndEquipmentNet" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/PropertyAndEquipmentNetDetails" xlink:href="qlys-20150630.xsd#PropertyAndEquipmentNetDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/PropertyAndEquipmentNetTables" xlink:href="qlys-20150630.xsd#PropertyAndEquipmentNetTables" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/SegmentInformationAndInformationAboutGeographicArea" xlink:href="qlys-20150630.xsd#SegmentInformationAndInformationAboutGeographicArea" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/SegmentInformationAndInformationAboutGeographicAreaDetails" xlink:href="qlys-20150630.xsd#SegmentInformationAndInformationAboutGeographicAreaDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/SegmentInformationAndInformationAboutGeographicAreaTables" xlink:href="qlys-20150630.xsd#SegmentInformationAndInformationAboutGeographicAreaTables" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/StockBasedCompensation" xlink:href="qlys-20150630.xsd#StockBasedCompensation" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/StockBasedCompensationExpenseDetails" xlink:href="qlys-20150630.xsd#StockBasedCompensationExpenseDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/StockBasedCompensationFairValueAssumptionsStockOptionsDetails" xlink:href="qlys-20150630.xsd#StockBasedCompensationFairValueAssumptionsStockOptionsDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/StockBasedCompensationRestrictedStockDetails" xlink:href="qlys-20150630.xsd#StockBasedCompensationRestrictedStockDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/StockBasedCompensationStockOptionPlanActivityDetails" xlink:href="qlys-20150630.xsd#StockBasedCompensationStockOptionPlanActivityDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/StockBasedCompensationStockOptionsDetails" xlink:href="qlys-20150630.xsd#StockBasedCompensationStockOptionsDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.qualys.com/role/StockBasedCompensationTables" xlink:href="qlys-20150630.xsd#StockBasedCompensationTables" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <definitionLink xlink:role="http://www.qualys.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CommitmentsAndContingenciesLeaseNarrativeDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CommitmentsAndContingenciesSalesAndOtherTaxesDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CommitmentsAndContingenciesScheduleOfLeasesDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CommitmentsAndContingenciesTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CompanyAndSummaryOfSignificantAccountingPolicies" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CompanyAndSummaryOfSignificantAccountingPoliciesCorrectionOfImmaterialErrorDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems" xlink:label="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable" xlink:label="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_83D3118E4861EA2B90E8FFEB1B7D197B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_83D3118E4861EA2B90E8FFEB1B7D197B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementScenarioAxis" xlink:label="loc_us-gaap_StatementScenarioAxis_D212B27862DE7037888DFFEB1B7D792B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_83D3118E4861EA2B90E8FFEB1B7D197B" xlink:to="loc_us-gaap_StatementScenarioAxis_D212B27862DE7037888DFFEB1B7D792B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_C2D98B48809FBD4E852BFFEB1B7D4AF0_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementScenarioAxis_D212B27862DE7037888DFFEB1B7D792B" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_C2D98B48809FBD4E852BFFEB1B7D4AF0_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_C2D98B48809FBD4E852BFFEB1B7D4AF0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementScenarioAxis_D212B27862DE7037888DFFEB1B7D792B" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_C2D98B48809FBD4E852BFFEB1B7D4AF0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScenarioPreviouslyReportedMember" xlink:label="loc_us-gaap_ScenarioPreviouslyReportedMember_46A044390404940FE090FFEB1B7D3EE8" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScenarioUnspecifiedDomain_C2D98B48809FBD4E852BFFEB1B7D4AF0" xlink:to="loc_us-gaap_ScenarioPreviouslyReportedMember_46A044390404940FE090FFEB1B7D3EE8" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScenarioAdjustmentMember" xlink:label="loc_us-gaap_ScenarioAdjustmentMember_EBB2859C46B14748855FFFEB1B7DE7A2" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScenarioUnspecifiedDomain_C2D98B48809FBD4E852BFFEB1B7D4AF0" xlink:to="loc_us-gaap_ScenarioAdjustmentMember_EBB2859C46B14748855FFFEB1B7DE7A2" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_BE785908B47F0AA8062FFFEB1B7E421C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_BE785908B47F0AA8062FFFEB1B7E421C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_47C51D2A234BE0DAB72FFFEB1B7ECA07" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_47C51D2A234BE0DAB72FFFEB1B7ECA07" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_DFCA5CF8E2D5682551DFFFEB1B7E43E3" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_NetIncomeLoss_DFCA5CF8E2D5682551DFFFEB1B7E43E3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_DBA70263DC7F5786B72DFFEB1B7E642B" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_EarningsPerShareBasic_DBA70263DC7F5786B72DFFEB1B7E642B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_94F76A1ACC4B36587F98FFEB1B7E3069" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_EarningsPerShareDiluted_94F76A1ACC4B36587F98FFEB1B7E3069" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_329D41AE65297A636D71FFEB1B7EBD61" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_329D41AE65297A636D71FFEB1B7EBD61" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_8E03B33FB34A7BBE2E75FFEB1B7E0A67" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_8E03B33FB34A7BBE2E75FFEB1B7E0A67" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_D68C700828066071EDF8FFEB1B7E80BE" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_D68C700828066071EDF8FFEB1B7E80BE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_5913F0B3FC3425F66ED1FFEB1B7EBC9E" xlink:type="locator" />
    <definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_5913F0B3FC3425F66ED1FFEB1B7EBC9E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_7A3D09E955CC6D6D6EB8FFEB1B7EAC70" xlink:type="locator" />
    <definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_7A3D09E955CC6D6D6EB8FFEB1B7EAC70" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:label="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease_816E70098503A73133AEFFEB1B7E712D" xlink:type="locator" />
    <definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_1F9DB23AB4F0428B2D87FFEB1B7D8180" xlink:to="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease_816E70098503A73133AEFFEB1B7E712D" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/CompanyAndSummaryOfSignificantAccountingPoliciesDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskLineItems" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_9ACEB6BDEB5E0078CFA1F92D4EF3E1FB" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskTable" xlink:label="loc_us-gaap_ConcentrationRiskTable_F85141F6567EA51E0724F92D4EF2D4A5" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_9ACEB6BDEB5E0078CFA1F92D4EF3E1FB" xlink:to="loc_us-gaap_ConcentrationRiskTable_F85141F6567EA51E0724F92D4EF2D4A5" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_80D310052D8AE5F0026FF92D4EF32024" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_F85141F6567EA51E0724F92D4EF2D4A5" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_80D310052D8AE5F0026FF92D4EF32024" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_9D140354465BBE76AFCCF92D4EF3BB1B_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_80D310052D8AE5F0026FF92D4EF32024" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_9D140354465BBE76AFCCF92D4EF3BB1B_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_9D140354465BBE76AFCCF92D4EF3BB1B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_80D310052D8AE5F0026FF92D4EF32024" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_9D140354465BBE76AFCCF92D4EF3BB1B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccountsReceivableMember" xlink:label="loc_us-gaap_AccountsReceivableMember_9740A3871F01F9EF1F44F92D4EF351AC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_9D140354465BBE76AFCCF92D4EF3BB1B" xlink:to="loc_us-gaap_AccountsReceivableMember_9740A3871F01F9EF1F44F92D4EF351AC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_656C829C42B48E69866DF92D4EF3B215" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_F85141F6567EA51E0724F92D4EF2D4A5" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_656C829C42B48E69866DF92D4EF3B215" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_3181562155DC99DDDDABF92D4EF3F44E_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_656C829C42B48E69866DF92D4EF3B215" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_3181562155DC99DDDDABF92D4EF3F44E_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_3181562155DC99DDDDABF92D4EF3F44E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_656C829C42B48E69866DF92D4EF3B215" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_3181562155DC99DDDDABF92D4EF3F44E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_9A71386BF2186C7475B8F92D4EF36892" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_3181562155DC99DDDDABF92D4EF3F44E" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_9A71386BF2186C7475B8F92D4EF36892" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_ConcentrationRiskNumberOfCustomers" xlink:label="loc_qlys_ConcentrationRiskNumberOfCustomers_80BA3F5621F8AED8FF1AF92D4EF316E0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_9ACEB6BDEB5E0078CFA1F92D4EF3E1FB" xlink:to="loc_qlys_ConcentrationRiskNumberOfCustomers_80BA3F5621F8AED8FF1AF92D4EF316E0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LandAndLandImprovementsAbstract" xlink:label="loc_us-gaap_LandAndLandImprovementsAbstract_7B02129E61904F401159F93A5D38DE84" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_9ACEB6BDEB5E0078CFA1F92D4EF3E1FB" xlink:to="loc_us-gaap_LandAndLandImprovementsAbstract_7B02129E61904F401159F93A5D38DE84" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CapitalizedComputerSoftwareGross" xlink:label="loc_us-gaap_CapitalizedComputerSoftwareGross_BA07ED504A3432108DAAF92D4EF34ABC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LandAndLandImprovementsAbstract_7B02129E61904F401159F93A5D38DE84" xlink:to="loc_us-gaap_CapitalizedComputerSoftwareGross_BA07ED504A3432108DAAF92D4EF34ABC" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/CompanyAndSummaryOfSignificantAccountingPoliciesPolicies" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CompanyAndSummaryOfSignificantAccountingPoliciesTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CondensedConsolidatedBalanceSheets" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CondensedConsolidatedBalanceSheetsParenthetical" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CondensedConsolidatedStatementsOfCashFlows" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CondensedConsolidatedStatementsOfComprehensiveIncome" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/CondensedConsolidatedStatementsOfOperations" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/DocumentAndEntityInformation" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/FairValueOfFinancialInstruments" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/FairValueOfFinancialInstrumentsCashAndCashEquivalentsAvailableForSaleSecuritiesReconciliationDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_669FF12C5B1A035542A2E557BE308A4D" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1583B377053F6B82F7BEE557BE2F8FA6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_669FF12C5B1A035542A2E557BE308A4D" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1583B377053F6B82F7BEE557BE2F8FA6" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_1387F628FF05A5141A24E557BE2F4609" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1583B377053F6B82F7BEE557BE2F8FA6" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_1387F628FF05A5141A24E557BE2F4609" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_F47A451C5D8305D016F8E557BE2FFD70_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_1387F628FF05A5141A24E557BE2F4609" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_F47A451C5D8305D016F8E557BE2FFD70_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_F47A451C5D8305D016F8E557BE2FFD70" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_1387F628FF05A5141A24E557BE2F4609" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_F47A451C5D8305D016F8E557BE2FFD70" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CashMember" xlink:label="loc_us-gaap_CashMember_9172D47D1B4C717A1585E557BE2FD36F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_F47A451C5D8305D016F8E557BE2FFD70" xlink:to="loc_us-gaap_CashMember_9172D47D1B4C717A1585E557BE2FD36F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MoneyMarketFundsMember" xlink:label="loc_us-gaap_MoneyMarketFundsMember_DF5B359AD71C13AD6C4DE557BE30204F" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_F47A451C5D8305D016F8E557BE2FFD70" xlink:to="loc_us-gaap_MoneyMarketFundsMember_DF5B359AD71C13AD6C4DE557BE30204F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CommercialPaperMember" xlink:label="loc_us-gaap_CommercialPaperMember_B97BB712D4A829315447E557BE302890" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_F47A451C5D8305D016F8E557BE2FFD70" xlink:to="loc_us-gaap_CommercialPaperMember_B97BB712D4A829315447E557BE302890" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CorporateBondSecuritiesMember" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_FC14F3D7AD6C1A952F4DE557BE302FB8" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_F47A451C5D8305D016F8E557BE2FFD70" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_FC14F3D7AD6C1A952F4DE557BE302FB8" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AssetBackedSecuritiesMember" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_722865F9CFFB21CEDD5BE557BE30400E" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_F47A451C5D8305D016F8E557BE2FFD70" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_722865F9CFFB21CEDD5BE557BE30400E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_834E78A578188E1DECF1E557BE302E83" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_F47A451C5D8305D016F8E557BE2FFD70" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_834E78A578188E1DECF1E557BE302E83" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_69195AA61BD2A7F54768E557BE3058BB" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1583B377053F6B82F7BEE557BE2F8FA6" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_69195AA61BD2A7F54768E557BE3058BB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_E605593A8A04A8682028E557BE307A70_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_69195AA61BD2A7F54768E557BE3058BB" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_E605593A8A04A8682028E557BE307A70_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_E605593A8A04A8682028E557BE307A70" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_69195AA61BD2A7F54768E557BE3058BB" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_E605593A8A04A8682028E557BE307A70" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CashAndCashEquivalentsMember" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_3E2FC6A77A4FE89D9373E557BE30963A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_E605593A8A04A8682028E557BE307A70" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_3E2FC6A77A4FE89D9373E557BE30963A" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_AvailableForSaleSecuritiesLineItemMember" xlink:label="loc_qlys_AvailableForSaleSecuritiesLineItemMember_9F8017A0B558FD1B84ABE557BE30CC2E" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_E605593A8A04A8682028E557BE307A70" xlink:to="loc_qlys_AvailableForSaleSecuritiesLineItemMember_9F8017A0B558FD1B84ABE557BE30CC2E" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_LongTermInvestmentsMember" xlink:label="loc_qlys_LongTermInvestmentsMember_D4D5A9DABA7BB6B9200BE557BE30B9CF" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_E605593A8A04A8682028E557BE307A70" xlink:to="loc_qlys_LongTermInvestmentsMember_D4D5A9DABA7BB6B9200BE557BE30B9CF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_3E616A89AC09CD779741E557BE302A60" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_669FF12C5B1A035542A2E557BE308A4D" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_3E616A89AC09CD779741E557BE302A60" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAmortizedCost" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_0FD245F2E39BAFF12ADCE557BE30D5D3" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_3E616A89AC09CD779741E557BE302A60" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_0FD245F2E39BAFF12ADCE557BE30D5D3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_4CF75028CA648715E80EE557BE30C25F" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_3E616A89AC09CD779741E557BE302A60" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_4CF75028CA648715E80EE557BE30C25F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_D0804A5DA4B2055A9407E557BE31DDC3" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_3E616A89AC09CD779741E557BE302A60" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_D0804A5DA4B2055A9407E557BE31DDC3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AvailableForSaleSecuritiesCurrent" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesCurrent_9B4A929847D11EE7294CE557BE31F1AD" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_3E616A89AC09CD779741E557BE302A60" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesCurrent_9B4A929847D11EE7294CE557BE31F1AD" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/FairValueOfFinancialInstrumentsContractualMaturityDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_37CE25D56EB6DBD111CFDCBA3F43F324" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_4D5E266ADEF9A6DE6E2DDCBA3F428386" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_37CE25D56EB6DBD111CFDCBA3F43F324" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_4D5E266ADEF9A6DE6E2DDCBA3F428386" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_D846B3922326F84026DCDCBA3F43ED15" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_4D5E266ADEF9A6DE6E2DDCBA3F428386" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_D846B3922326F84026DCDCBA3F43ED15" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_D5513158F9FA9BF87D52DCBA3F4361BB_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_D846B3922326F84026DCDCBA3F43ED15" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_D5513158F9FA9BF87D52DCBA3F4361BB_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_D5513158F9FA9BF87D52DCBA3F4361BB" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_D846B3922326F84026DCDCBA3F43ED15" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_D5513158F9FA9BF87D52DCBA3F4361BB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CommercialPaperMember" xlink:label="loc_us-gaap_CommercialPaperMember_63C19651043DEEC78E4CDCBA3F43004C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_D5513158F9FA9BF87D52DCBA3F4361BB" xlink:to="loc_us-gaap_CommercialPaperMember_63C19651043DEEC78E4CDCBA3F43004C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_5B4B9A6D87214E21BE63DCBA3F431377" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_D5513158F9FA9BF87D52DCBA3F4361BB" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_5B4B9A6D87214E21BE63DCBA3F431377" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CorporateBondSecuritiesMember" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_DA831BB52088DBEA66E5DCBA3F4387FD" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_D5513158F9FA9BF87D52DCBA3F4361BB" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_DA831BB52088DBEA66E5DCBA3F4387FD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AssetBackedSecuritiesMember" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_58238860A3F87DA3658BDCBA3F4396C2" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_D5513158F9FA9BF87D52DCBA3F4361BB" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_58238860A3F87DA3658BDCBA3F4396C2" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue" xlink:label="loc_qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue_7F6E34B92DDFFF54604BDCBA3F43B68E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_37CE25D56EB6DBD111CFDCBA3F43F324" xlink:to="loc_qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue_7F6E34B92DDFFF54604BDCBA3F43B68E" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue" xlink:label="loc_qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue_EB697FCDB5DB9CE22213DCBA3F434D46" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_37CE25D56EB6DBD111CFDCBA3F43F324" xlink:to="loc_qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue_EB697FCDB5DB9CE22213DCBA3F434D46" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue" xlink:label="loc_qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue_763670FF21DF76D24E72DCBA3F432C67" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_37CE25D56EB6DBD111CFDCBA3F43F324" xlink:to="loc_qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue_763670FF21DF76D24E72DCBA3F432C67" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecurities_38FDEE6C026CF88BB6BCDCBA3F43DC2B" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_37CE25D56EB6DBD111CFDCBA3F43F324" xlink:to="loc_us-gaap_AvailableForSaleSecurities_38FDEE6C026CF88BB6BCDCBA3F43DC2B" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/FairValueOfFinancialInstrumentsDerivativesDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DerivativesFairValueLineItems" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_1BE7B6013038FB3DCF83DCBA3F6D2382" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_56A175703ADFFDBC265FDCBA3F6BACF0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_1BE7B6013038FB3DCF83DCBA3F6D2382" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_56A175703ADFFDBC265FDCBA3F6BACF0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DerivativeByNatureAxis" xlink:label="loc_us-gaap_DerivativeByNatureAxis_8EE2A45A0B26DDC372E7DCBA3F6C7856" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_56A175703ADFFDBC265FDCBA3F6BACF0" xlink:to="loc_us-gaap_DerivativeByNatureAxis_8EE2A45A0B26DDC372E7DCBA3F6C7856" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DerivativeNameDomain" xlink:label="loc_us-gaap_DerivativeNameDomain_8A1FE16FF63E79AEA9CEDCBA3F6D8EB7_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeByNatureAxis_8EE2A45A0B26DDC372E7DCBA3F6C7856" xlink:to="loc_us-gaap_DerivativeNameDomain_8A1FE16FF63E79AEA9CEDCBA3F6D8EB7_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DerivativeNameDomain" xlink:label="loc_us-gaap_DerivativeNameDomain_8A1FE16FF63E79AEA9CEDCBA3F6D8EB7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeByNatureAxis_8EE2A45A0B26DDC372E7DCBA3F6C7856" xlink:to="loc_us-gaap_DerivativeNameDomain_8A1FE16FF63E79AEA9CEDCBA3F6D8EB7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ForwardContractsMember" xlink:label="loc_us-gaap_ForwardContractsMember_13E595347EB22BB1C89ADCBA3F6D7DE4" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeNameDomain_8A1FE16FF63E79AEA9CEDCBA3F6D8EB7" xlink:to="loc_us-gaap_ForwardContractsMember_13E595347EB22BB1C89ADCBA3F6D7DE4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DerivativeNumberOfInstrumentsHeld" xlink:label="loc_us-gaap_DerivativeNumberOfInstrumentsHeld_5BDCA72138C0708D49FDDCBA3F6D62A0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_1BE7B6013038FB3DCF83DCBA3F6D2382" xlink:to="loc_us-gaap_DerivativeNumberOfInstrumentsHeld_5BDCA72138C0708D49FDDCBA3F6D62A0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd#invest_DerivativeNotionalAmount" xlink:label="loc_invest_DerivativeNotionalAmount_F4937859AA56616E941FDCBA3F6D7B4B" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_1BE7B6013038FB3DCF83DCBA3F6D2382" xlink:to="loc_invest_DerivativeNotionalAmount_F4937859AA56616E941FDCBA3F6D7B4B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ForeignCurrencyContractAssetFairValueDisclosure" xlink:label="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_2B69172FD79F779FD54BDCBA3F6D69EB" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_1BE7B6013038FB3DCF83DCBA3F6D2382" xlink:to="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_2B69172FD79F779FD54BDCBA3F6D69EB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLoss" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLoss_9D752E50E4DB024D7286DCBA3F6DAE70" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_1BE7B6013038FB3DCF83DCBA3F6D2382" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLoss_9D752E50E4DB024D7286DCBA3F6DAE70" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainBeforeTax" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainBeforeTax_FB6ADE4D9E65B31E571FDCBA3F6D5477" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_1BE7B6013038FB3DCF83DCBA3F6D2382" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainBeforeTax_FB6ADE4D9E65B31E571FDCBA3F6D5477" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGain" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGain_EAA266068A4B57A21209DCBA3F6DAE7F" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_1BE7B6013038FB3DCF83DCBA3F6D2382" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGain_EAA266068A4B57A21209DCBA3F6DAE7F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ForeignCurrencyTransactionLossBeforeTax" xlink:label="loc_us-gaap_ForeignCurrencyTransactionLossBeforeTax_6409CD0B69D6883422D7DCBA3F6D4220" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_1BE7B6013038FB3DCF83DCBA3F6D2382" xlink:to="loc_us-gaap_ForeignCurrencyTransactionLossBeforeTax_6409CD0B69D6883422D7DCBA3F6D4220" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/FairValueOfFinancialInstrumentsFairValueHierarchyDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_DCD1FD08E865443CFE4BDCBA3F3D5667" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93C111D223CCB1CCAAFCDCBA3F3C29E4" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_DCD1FD08E865443CFE4BDCBA3F3D5667" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93C111D223CCB1CCAAFCDCBA3F3C29E4" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_43546D75937B152E93F5DCBA3F3C24DB" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93C111D223CCB1CCAAFCDCBA3F3C29E4" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_43546D75937B152E93F5DCBA3F3C24DB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_75721C80AE93867A92F1DCBA3F3CF92F_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_43546D75937B152E93F5DCBA3F3C24DB" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_75721C80AE93867A92F1DCBA3F3CF92F_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_EAC008490CA270969965DCBA3F3C2B53" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_43546D75937B152E93F5DCBA3F3C24DB" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_EAC008490CA270969965DCBA3F3C2B53" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_75721C80AE93867A92F1DCBA3F3CF92F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_EAC008490CA270969965DCBA3F3C2B53" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_75721C80AE93867A92F1DCBA3F3CF92F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_221126F4D2B3D1A8A196DCBA3F3CFDC6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_75721C80AE93867A92F1DCBA3F3CF92F" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_221126F4D2B3D1A8A196DCBA3F3CFDC6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_0F8A70936F6A5C28EBF3DCBA3F3C5034" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93C111D223CCB1CCAAFCDCBA3F3C29E4" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_0F8A70936F6A5C28EBF3DCBA3F3C5034" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_81147033C29B6792DF9BDCBA3F3C4162_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_0F8A70936F6A5C28EBF3DCBA3F3C5034" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_81147033C29B6792DF9BDCBA3F3C4162_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_81147033C29B6792DF9BDCBA3F3C4162" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_0F8A70936F6A5C28EBF3DCBA3F3C5034" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_81147033C29B6792DF9BDCBA3F3C4162" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CommercialPaperMember" xlink:label="loc_us-gaap_CommercialPaperMember_EE395A2BC3766BC15D2EDCBA3F3C4FF9" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_81147033C29B6792DF9BDCBA3F3C4162" xlink:to="loc_us-gaap_CommercialPaperMember_EE395A2BC3766BC15D2EDCBA3F3C4FF9" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_031ACE99E4573903830ADCBA3F3C13C1" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_81147033C29B6792DF9BDCBA3F3C4162" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_031ACE99E4573903830ADCBA3F3C13C1" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CorporateBondSecuritiesMember" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_AD263F6E3852E5A1CC8DDCBA3F3CBD6D" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_81147033C29B6792DF9BDCBA3F3C4162" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_AD263F6E3852E5A1CC8DDCBA3F3CBD6D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AssetBackedSecuritiesMember" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_6A4D95E7F1C1D8D25140DCBA3F3C22D2" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_81147033C29B6792DF9BDCBA3F3C4162" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_6A4D95E7F1C1D8D25140DCBA3F3C22D2" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_FEE62B58E61EE91B41BCDCBA3F3CEAB3" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93C111D223CCB1CCAAFCDCBA3F3C29E4" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_FEE62B58E61EE91B41BCDCBA3F3CEAB3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3AF1F1C742CD0BC2F820DCBA3F3D2054_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_FEE62B58E61EE91B41BCDCBA3F3CEAB3" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3AF1F1C742CD0BC2F820DCBA3F3D2054_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3AF1F1C742CD0BC2F820DCBA3F3D2054" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_FEE62B58E61EE91B41BCDCBA3F3CEAB3" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3AF1F1C742CD0BC2F820DCBA3F3D2054" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_F02A4A296D31B4BF131EDCBA3F3D0536" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3AF1F1C742CD0BC2F820DCBA3F3D2054" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_F02A4A296D31B4BF131EDCBA3F3D0536" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_A23788A0F811D9DE69EEDCBA3F3DB900" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3AF1F1C742CD0BC2F820DCBA3F3D2054" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_A23788A0F811D9DE69EEDCBA3F3DB900" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_D939B7C28CE4244940FFDCBA3F3D3568" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3AF1F1C742CD0BC2F820DCBA3F3D2054" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_D939B7C28CE4244940FFDCBA3F3D3568" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_80974B6BD39F99C162CBDCBA3F3DD1E1" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93C111D223CCB1CCAAFCDCBA3F3C29E4" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_80974B6BD39F99C162CBDCBA3F3DD1E1" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_E98CF4CC96839CC22451DCBA3F3D0A08_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_80974B6BD39F99C162CBDCBA3F3DD1E1" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_E98CF4CC96839CC22451DCBA3F3D0A08_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_E98CF4CC96839CC22451DCBA3F3D0A08" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_80974B6BD39F99C162CBDCBA3F3DD1E1" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_E98CF4CC96839CC22451DCBA3F3D0A08" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_3A3416FED700C0259C3ADCBA3F3DC2EC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_E98CF4CC96839CC22451DCBA3F3D0A08" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_3A3416FED700C0259C3ADCBA3F3DC2EC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AssetsFairValueDisclosureAbstract" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_83D70F92C8EF4CCB6776DCBA3F3DB116" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_DCD1FD08E865443CFE4BDCBA3F3D5667" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_83D70F92C8EF4CCB6776DCBA3F3DB116" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecurities_2AAC1DC7EA99DB977D05DCBA3F3D92CB" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_83D70F92C8EF4CCB6776DCBA3F3DB116" xlink:to="loc_us-gaap_AvailableForSaleSecurities_2AAC1DC7EA99DB977D05DCBA3F3D92CB" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/FairValueOfFinancialInstrumentsTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/GoodwillAndIntangibleAssetsNet" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/GoodwillAndIntangibleAssetsNetDetails" xlink:type="extended">
    <loc xlink:href="qlys-20150630.xsd#qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems" xlink:label="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems_298306F934900497015EDCBA991C05FD" xlink:type="locator" />
    <loc xlink:href="qlys-20150630.xsd#qlys_ScheduleOfGoodwillAndIntangibleAssetsTable" xlink:label="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsTable_C520C46358FBA08F1BBFDCBA991A8E0C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems_298306F934900497015EDCBA991C05FD" xlink:to="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsTable_C520C46358FBA08F1BBFDCBA991A8E0C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_6C9214F083D008B95292DCBA991A1B41" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsTable_C520C46358FBA08F1BBFDCBA991A8E0C" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_6C9214F083D008B95292DCBA991A1B41" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88DA7D7806C65728332BDCBA991A22E8_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_6C9214F083D008B95292DCBA991A1B41" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88DA7D7806C65728332BDCBA991A22E8_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88DA7D7806C65728332BDCBA991A22E8" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_6C9214F083D008B95292DCBA991A1B41" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88DA7D7806C65728332BDCBA991A22E8" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_00F79979E47AE3FB1782DCBA991AB05D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88DA7D7806C65728332BDCBA991A22E8" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_00F79979E47AE3FB1782DCBA991AB05D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PatentsMember" xlink:label="loc_us-gaap_PatentsMember_CCB3CC18FE4DEEB82F40DCBA991B93F3" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88DA7D7806C65728332BDCBA991A22E8" xlink:to="loc_us-gaap_PatentsMember_CCB3CC18FE4DEEB82F40DCBA991B93F3" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_NonCompetitionAgreementsAndOtherIntangibleAssetsMemberMember" xlink:label="loc_qlys_NonCompetitionAgreementsAndOtherIntangibleAssetsMemberMember_E126E6FF3516027D0752DCBA991B48AC" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88DA7D7806C65728332BDCBA991A22E8" xlink:to="loc_qlys_NonCompetitionAgreementsAndOtherIntangibleAssetsMemberMember_E126E6FF3516027D0752DCBA991B48AC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_C8446722EC5EE6642AA5DCBA991C89F7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems_298306F934900497015EDCBA991C05FD" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_C8446722EC5EE6642AA5DCBA991C89F7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_DF9518E31594E30E2764DCBA991C79EB" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems_298306F934900497015EDCBA991C05FD" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_DF9518E31594E30E2764DCBA991C79EB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_2DC133AD555FA34BA73EDCBA991C4C0F" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems_298306F934900497015EDCBA991C05FD" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_2DC133AD555FA34BA73EDCBA991C4C0F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_354C09C155E5FE027292DCBA991CB226" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems_298306F934900497015EDCBA991C05FD" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_354C09C155E5FE027292DCBA991CB226" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_21049301E7FBBAB9F87EDCBA991C7815" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems_298306F934900497015EDCBA991C05FD" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_21049301E7FBBAB9F87EDCBA991C7815" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_B3A9DB3EBF458C829FF0DCBA991C7501" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems_298306F934900497015EDCBA991C05FD" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_B3A9DB3EBF458C829FF0DCBA991C7501" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_F5EA452B72DED98C1E09DCBA991C4D25" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems_298306F934900497015EDCBA991C05FD" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_F5EA452B72DED98C1E09DCBA991C4D25" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_7BEE1BC4D3C54777687FDCBA991CF5C9" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_ScheduleOfGoodwillAndIntangibleAssetsLineItems_298306F934900497015EDCBA991C05FD" xlink:to="loc_us-gaap_Goodwill_7BEE1BC4D3C54777687FDCBA991CF5C9" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/GoodwillAndIntangibleAssetsNetFutureAmortizationDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/GoodwillAndIntangibleAssetsNetTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/IncomeTaxes" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/IncomeTaxesDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/NetIncomePerShare" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/NetIncomePerShareDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_F54EF46F57E476EDE3AFE5B9B4993DAD" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_EFE14FF55937763659F5E5B9B4989482" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_F54EF46F57E476EDE3AFE5B9B4993DAD" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_EFE14FF55937763659F5E5B9B4989482" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_ECC4E655E3951327D39EE5B9B498EC01" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_EFE14FF55937763659F5E5B9B4989482" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_ECC4E655E3951327D39EE5B9B498EC01" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_917D8D21D0A76EFB615BE5B9B4999A7A_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_ECC4E655E3951327D39EE5B9B498EC01" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_917D8D21D0A76EFB615BE5B9B4999A7A_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_917D8D21D0A76EFB615BE5B9B4999A7A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_ECC4E655E3951327D39EE5B9B498EC01" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_917D8D21D0A76EFB615BE5B9B4999A7A" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_7387DF7C905E71C5F5FEE5B9B499D9FD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_917D8D21D0A76EFB615BE5B9B4999A7A" xlink:to="loc_us-gaap_EmployeeStockOptionMember_7387DF7C905E71C5F5FEE5B9B499D9FD" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_NumeratorAbstract" xlink:label="loc_qlys_NumeratorAbstract_6F6A4019762E2852E839E5B9B4994520" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_F54EF46F57E476EDE3AFE5B9B4993DAD" xlink:to="loc_qlys_NumeratorAbstract_6F6A4019762E2852E839E5B9B4994520" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_59391CC74C329BA7F691E5B9B49906FA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_NumeratorAbstract_6F6A4019762E2852E839E5B9B4994520" xlink:to="loc_us-gaap_NetIncomeLoss_59391CC74C329BA7F691E5B9B49906FA" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_DenominatorAbstract" xlink:label="loc_qlys_DenominatorAbstract_A0EF2F17EBA77F03713AE5B9B499D69E" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_F54EF46F57E476EDE3AFE5B9B4993DAD" xlink:to="loc_qlys_DenominatorAbstract_A0EF2F17EBA77F03713AE5B9B499D69E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_9D085F74B4832B39B22DE5B9B499C3DE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_DenominatorAbstract_A0EF2F17EBA77F03713AE5B9B499D69E" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_9D085F74B4832B39B22DE5B9B499C3DE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_49DF5FDED4D99365AE99E5B9B4991B6F" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_DenominatorAbstract_A0EF2F17EBA77F03713AE5B9B499D69E" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_49DF5FDED4D99365AE99E5B9B4991B6F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_02F00B6B99BE8B6DA6DEE5B9B499AE8F" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_DenominatorAbstract_A0EF2F17EBA77F03713AE5B9B499D69E" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_02F00B6B99BE8B6DA6DEE5B9B499AE8F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_4C2D29FFAAA06809F1C4E5B9B4992047" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_F54EF46F57E476EDE3AFE5B9B4993DAD" xlink:to="loc_us-gaap_EarningsPerShareBasic_4C2D29FFAAA06809F1C4E5B9B4992047" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_1842CA5DA07BF434A417E5B9B499F916" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_F54EF46F57E476EDE3AFE5B9B4993DAD" xlink:to="loc_us-gaap_EarningsPerShareDiluted_1842CA5DA07BF434A417E5B9B499F916" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_AntidilutiveSecuritiesAbstract" xlink:label="loc_qlys_AntidilutiveSecuritiesAbstract_F7161E368DC02543243BE5B9B499C1A5" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_F54EF46F57E476EDE3AFE5B9B4993DAD" xlink:to="loc_qlys_AntidilutiveSecuritiesAbstract_F7161E368DC02543243BE5B9B499C1A5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_8095E00FA833B09C9858E5B9B499C7BA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_AntidilutiveSecuritiesAbstract_F7161E368DC02543243BE5B9B499C1A5" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_8095E00FA833B09C9858E5B9B499C7BA" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/NetIncomePerShareTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/OtherIncomeExpenseNet" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/OtherIncomeExpenseNetDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/OtherIncomeExpenseNetTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/PropertyAndEquipmentNet" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/PropertyAndEquipmentNetDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_450E276E41E7F222C458DCBA78AD3A30" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_539FA5AC7963D2F09654DCBA78AD1103" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_450E276E41E7F222C458DCBA78AD3A30" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_539FA5AC7963D2F09654DCBA78AD1103" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3290A78E22E065B3AD92DCBA78ADCD90" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_539FA5AC7963D2F09654DCBA78AD1103" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3290A78E22E065B3AD92DCBA78ADCD90" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1A08203277474DCC00BEDCBA78AD6530_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3290A78E22E065B3AD92DCBA78ADCD90" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1A08203277474DCC00BEDCBA78AD6530_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1A08203277474DCC00BEDCBA78AD6530" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3290A78E22E065B3AD92DCBA78ADCD90" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1A08203277474DCC00BEDCBA78AD6530" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ComputerEquipmentMember" xlink:label="loc_us-gaap_ComputerEquipmentMember_3B4AB1F2975D14B7388EDCBA78AD9E2F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1A08203277474DCC00BEDCBA78AD6530" xlink:to="loc_us-gaap_ComputerEquipmentMember_3B4AB1F2975D14B7388EDCBA78AD9E2F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_9C13FE33E9078F165DBEDCBA78AD3B7E" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1A08203277474DCC00BEDCBA78AD6530" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_9C13FE33E9078F165DBEDCBA78AD3B7E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FurnitureAndFixturesMember" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_D896038E4BF398F69B55DCBA78AD560F" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1A08203277474DCC00BEDCBA78AD6530" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_D896038E4BF398F69B55DCBA78AD560F" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_ScannerAppliancesMember" xlink:label="loc_qlys_ScannerAppliancesMember_81816BAA8CA1315A774DDCBA78ADDBB2" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1A08203277474DCC00BEDCBA78AD6530" xlink:to="loc_qlys_ScannerAppliancesMember_81816BAA8CA1315A774DDCBA78ADDBB2" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_ScannerAppliancesAndOtherComputerEquipmentSubjectToSubscriptionMember" xlink:label="loc_qlys_ScannerAppliancesAndOtherComputerEquipmentSubjectToSubscriptionMember_FE104804D1A3D760975ADCBA78ADE9C8" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_ScannerAppliancesMember_81816BAA8CA1315A774DDCBA78ADDBB2" xlink:to="loc_qlys_ScannerAppliancesAndOtherComputerEquipmentSubjectToSubscriptionMember_FE104804D1A3D760975ADCBA78ADE9C8" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_ScannerAppliancesAndOtherComputerEquipmentNotPlacedInServiceMember" xlink:label="loc_qlys_ScannerAppliancesAndOtherComputerEquipmentNotPlacedInServiceMember_6DF5F2CC69E4458B2110DCBA78AD77B4" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_qlys_ScannerAppliancesMember_81816BAA8CA1315A774DDCBA78ADDBB2" xlink:to="loc_qlys_ScannerAppliancesAndOtherComputerEquipmentNotPlacedInServiceMember_6DF5F2CC69E4458B2110DCBA78AD77B4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_9B096B9773517C69C733DCBA78AD84BB" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1A08203277474DCC00BEDCBA78AD6530" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_9B096B9773517C69C733DCBA78AD84BB" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_OtherFixedAssetsNotPlacedInServiceMember" xlink:label="loc_qlys_OtherFixedAssetsNotPlacedInServiceMember_FE4856B62E0ED4A59440DCBA78AD5474" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1A08203277474DCC00BEDCBA78AD6530" xlink:to="loc_qlys_OtherFixedAssetsNotPlacedInServiceMember_FE4856B62E0ED4A59440DCBA78AD5474" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_43612277416CDE1723D1DCBA78AD186E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_450E276E41E7F222C458DCBA78AD3A30" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_43612277416CDE1723D1DCBA78AD186E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_A71E32C640C481BCF3CDDCBA78AD2D3E" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_450E276E41E7F222C458DCBA78AD3A30" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_A71E32C640C481BCF3CDDCBA78AD2D3E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_647077EC5F6B8F9FC171DCBA78AEF659" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_450E276E41E7F222C458DCBA78AD3A30" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_647077EC5F6B8F9FC171DCBA78AEF659" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_DepreciationDepletionAndAmortizationExcludingIntangibleAssetAmortization" xlink:label="loc_qlys_DepreciationDepletionAndAmortizationExcludingIntangibleAssetAmortization_259F179C312620F4860CDCBA78AE3E78" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_450E276E41E7F222C458DCBA78AD3A30" xlink:to="loc_qlys_DepreciationDepletionAndAmortizationExcludingIntangibleAssetAmortization_259F179C312620F4860CDCBA78AE3E78" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/PropertyAndEquipmentNetTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/SegmentInformationAndInformationAboutGeographicArea" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/SegmentInformationAndInformationAboutGeographicAreaDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_FD8AD9505783EB1391C0DCC268C2A84E" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4072270BE90F228E79BFDCC268C0C87E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_FD8AD9505783EB1391C0DCC268C2A84E" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4072270BE90F228E79BFDCC268C0C87E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementGeographicalAxis" xlink:label="loc_us-gaap_StatementGeographicalAxis_C3EF43E3B1AC0C407FFADCC268C18F5F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4072270BE90F228E79BFDCC268C0C87E" xlink:to="loc_us-gaap_StatementGeographicalAxis_C3EF43E3B1AC0C407FFADCC268C18F5F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="loc_us-gaap_SegmentGeographicalDomain_B5CB507411EB8B6419A4DCC268C1A4CC_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementGeographicalAxis_C3EF43E3B1AC0C407FFADCC268C18F5F" xlink:to="loc_us-gaap_SegmentGeographicalDomain_B5CB507411EB8B6419A4DCC268C1A4CC_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="loc_us-gaap_SegmentGeographicalDomain_B5CB507411EB8B6419A4DCC268C1A4CC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementGeographicalAxis_C3EF43E3B1AC0C407FFADCC268C18F5F" xlink:to="loc_us-gaap_SegmentGeographicalDomain_B5CB507411EB8B6419A4DCC268C1A4CC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/country/2013/country-2013-01-31.xsd#country_US" xlink:label="loc_country_US_74063148CA58BF7962E3DCC268C1CB1B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_B5CB507411EB8B6419A4DCC268C1A4CC" xlink:to="loc_country_US_74063148CA58BF7962E3DCC268C1CB1B" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_OtherGeographicAreasMember" xlink:label="loc_qlys_OtherGeographicAreasMember_EC53478B82822261EB49DCC268C269A4" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_B5CB507411EB8B6419A4DCC268C1A4CC" xlink:to="loc_qlys_OtherGeographicAreasMember_EC53478B82822261EB49DCC268C269A4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NumberOfOperatingSegments" xlink:label="loc_us-gaap_NumberOfOperatingSegments_5B8B30591D155917050FDCC268C23869" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_FD8AD9505783EB1391C0DCC268C2A84E" xlink:to="loc_us-gaap_NumberOfOperatingSegments_5B8B30591D155917050FDCC268C23869" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_F61F8D88AD2280C02329DCC268C22D96" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_FD8AD9505783EB1391C0DCC268C2A84E" xlink:to="loc_us-gaap_Revenues_F61F8D88AD2280C02329DCC268C22D96" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_9789537921181BCC851CDCC268C29310" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_FD8AD9505783EB1391C0DCC268C2A84E" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_9789537921181BCC851CDCC268C29310" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/SegmentInformationAndInformationAboutGeographicAreaTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/StockBasedCompensation" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/StockBasedCompensationExpenseDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_E13F0FA993F1586634DFE72420202BFC" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_4AA244724F9C6D7B0168E724201F97E3" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_E13F0FA993F1586634DFE72420202BFC" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_4AA244724F9C6D7B0168E724201F97E3" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_69D00F3324DA20F4D01EE724201FF97C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_4AA244724F9C6D7B0168E724201F97E3" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_69D00F3324DA20F4D01EE724201FF97C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_D2173796D3D3D65B13D2E724201F363E_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_69D00F3324DA20F4D01EE724201FF97C" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_D2173796D3D3D65B13D2E724201F363E_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_D2173796D3D3D65B13D2E724201F363E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_69D00F3324DA20F4D01EE724201FF97C" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_D2173796D3D3D65B13D2E724201F363E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CostOfSalesMember" xlink:label="loc_us-gaap_CostOfSalesMember_D7003A7929B83BD0F485E724201F7569" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_D2173796D3D3D65B13D2E724201F363E" xlink:to="loc_us-gaap_CostOfSalesMember_D7003A7929B83BD0F485E724201F7569" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_0AFEE04444DC631471BAE7242020D847" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_D2173796D3D3D65B13D2E724201F363E" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_0AFEE04444DC631471BAE7242020D847" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SellingAndMarketingExpenseMember" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_4C0AE67E50D069E5D420E72420208CB3" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_D2173796D3D3D65B13D2E724201F363E" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_4C0AE67E50D069E5D420E72420208CB3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_3D51066EDA48FABC436CE72420203F48" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_D2173796D3D3D65B13D2E724201F363E" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_3D51066EDA48FABC436CE72420203F48" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_F31B6F5FDDCA1C1B0FE3E7242020D83C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_E13F0FA993F1586634DFE72420202BFC" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_F31B6F5FDDCA1C1B0FE3E7242020D83C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_C897CC16F4352EB0617DE72420204321" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_E13F0FA993F1586634DFE72420202BFC" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_C897CC16F4352EB0617DE72420204321" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_A2DD9CF23375FDAD3097E7242020D90D" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_E13F0FA993F1586634DFE72420202BFC" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_A2DD9CF23375FDAD3097E7242020D90D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims" xlink:label="loc_us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims_276147FF86D74BCD1216E7242020C63D" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_E13F0FA993F1586634DFE72420202BFC" xlink:to="loc_us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims_276147FF86D74BCD1216E7242020C63D" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/StockBasedCompensationFairValueAssumptionsStockOptionsDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_40E44E0F8DF927D6630DE724201CE957" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_106531F21553EA18A82AE724201C4E2A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_40E44E0F8DF927D6630DE724201CE957" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_106531F21553EA18A82AE724201C4E2A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_837D724F3790F7A0FA0FE724201C8045" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_106531F21553EA18A82AE724201C4E2A" xlink:to="loc_us-gaap_RangeAxis_837D724F3790F7A0FA0FE724201C8045" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_07B6DC564836B32248D8E724201C5D02_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_837D724F3790F7A0FA0FE724201C8045" xlink:to="loc_us-gaap_RangeMember_07B6DC564836B32248D8E724201C5D02_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_07B6DC564836B32248D8E724201C5D02" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_837D724F3790F7A0FA0FE724201C8045" xlink:to="loc_us-gaap_RangeMember_07B6DC564836B32248D8E724201C5D02" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_D35A9B336636E3962B3CE724201C26EF" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_07B6DC564836B32248D8E724201C5D02" xlink:to="loc_us-gaap_MinimumMember_D35A9B336636E3962B3CE724201C26EF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_BBBA8DF7748C0A1C770EE724201C3A10" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_07B6DC564836B32248D8E724201C5D02" xlink:to="loc_us-gaap_MaximumMember_BBBA8DF7748C0A1C770EE724201C3A10" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_63CE7B4F0FB65426894BE724201CC671" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_106531F21553EA18A82AE724201C4E2A" xlink:to="loc_us-gaap_AwardTypeAxis_63CE7B4F0FB65426894BE724201CC671" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92CA8FB90665DF487128E724201CA1B6_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_63CE7B4F0FB65426894BE724201CC671" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92CA8FB90665DF487128E724201CA1B6_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92CA8FB90665DF487128E724201CA1B6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_63CE7B4F0FB65426894BE724201CC671" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92CA8FB90665DF487128E724201CA1B6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_01959B3640DB58CA0C17E724201C5E2D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92CA8FB90665DF487128E724201CA1B6" xlink:to="loc_us-gaap_EmployeeStockOptionMember_01959B3640DB58CA0C17E724201C5E2D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_0B9E995F7C5E0DABAF00E724201C4DD1" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_40E44E0F8DF927D6630DE724201CE957" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_0B9E995F7C5E0DABAF00E724201C4DD1" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_E26AB9EA58DB6E1C5709E724201C72D2" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_40E44E0F8DF927D6630DE724201CE957" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_E26AB9EA58DB6E1C5709E724201C72D2" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_F67DD5CB12B5B529B5B8E724201C40B1" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_40E44E0F8DF927D6630DE724201CE957" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_F67DD5CB12B5B529B5B8E724201C40B1" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_90DDC873193A9A138FB7E724201C1629" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_40E44E0F8DF927D6630DE724201CE957" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_90DDC873193A9A138FB7E724201C1629" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/StockBasedCompensationRestrictedStockDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_896DA02A88A68D2C556EE7242011027D" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_B4D66BF9D23097F893ABE72420118D04" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_896DA02A88A68D2C556EE7242011027D" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_B4D66BF9D23097F893ABE72420118D04" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_E52CE7AD2E58602833A3E72420112FE7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_B4D66BF9D23097F893ABE72420118D04" xlink:to="loc_us-gaap_AwardTypeAxis_E52CE7AD2E58602833A3E72420112FE7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0A3B3A957E8E3E73CAC0E72420113733_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_E52CE7AD2E58602833A3E72420112FE7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0A3B3A957E8E3E73CAC0E72420113733_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0A3B3A957E8E3E73CAC0E72420113733" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_E52CE7AD2E58602833A3E72420112FE7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0A3B3A957E8E3E73CAC0E72420113733" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="loc_us-gaap_RestrictedStockMember_FBAD5464F54BDFF9CB94E7242011C120" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0A3B3A957E8E3E73CAC0E72420113733" xlink:to="loc_us-gaap_RestrictedStockMember_FBAD5464F54BDFF9CB94E7242011C120" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_98113E482AFAE4356B6CE7242011F597" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_896DA02A88A68D2C556EE7242011027D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_98113E482AFAE4356B6CE7242011F597" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_35BF7CA9558DDB2A113FE72420113ED7" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_896DA02A88A68D2C556EE7242011027D" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_35BF7CA9558DDB2A113FE72420113ED7" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/StockBasedCompensationStockOptionPlanActivityDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.qualys.com/role/StockBasedCompensationStockOptionsDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9B9D46872729D458EC95E72420220706" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D0986F9334E2FB1938A6E72420224499" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9B9D46872729D458EC95E72420220706" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D0986F9334E2FB1938A6E72420224499" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_3F47162473022A12D2F1E7242022FDC7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D0986F9334E2FB1938A6E72420224499" xlink:to="loc_us-gaap_PlanNameAxis_3F47162473022A12D2F1E7242022FDC7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_C6FC85C03F32DB3C407FE7242022589F_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_3F47162473022A12D2F1E7242022FDC7" xlink:to="loc_us-gaap_PlanNameDomain_C6FC85C03F32DB3C407FE7242022589F_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_C6FC85C03F32DB3C407FE7242022589F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_3F47162473022A12D2F1E7242022FDC7" xlink:to="loc_us-gaap_PlanNameDomain_C6FC85C03F32DB3C407FE7242022589F" xlink:type="arc" />
    <loc xlink:href="qlys-20150630.xsd#qlys_A2012EquityIncentivePlanMember" xlink:label="loc_qlys_A2012EquityIncentivePlanMember_3C9E63F1DDB6AF9FA0EBE7242022C7BD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_C6FC85C03F32DB3C407FE7242022589F" xlink:to="loc_qlys_A2012EquityIncentivePlanMember_3C9E63F1DDB6AF9FA0EBE7242022C7BD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_2A3D2CDD579D95CA49EDE7242023F5BD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9B9D46872729D458EC95E72420220706" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_2A3D2CDD579D95CA49EDE7242023F5BD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_BADD3EABF7577EEFB3DBE7242023330A" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9B9D46872729D458EC95E72420220706" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_BADD3EABF7577EEFB3DBE7242023330A" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.qualys.com/role/StockBasedCompensationTables" xlink:type="extended" />
</linkbase>
