<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2019-07-11</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001013237</issuerCik>
        <issuerName>FACTSET RESEARCH SYSTEMS INC</issuerName>
        <issuerTradingSymbol>FDS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001782865</rptOwnerCik>
            <rptOwnerName>Moskoff Gregory T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FACTSET RESEARCH SYSTEMS INC.</rptOwnerStreet1>
            <rptOwnerStreet2>601 MERRITT 7</rptOwnerStreet2>
            <rptOwnerCity>NORWALK</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06851</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>SVP, Controller, PAO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <remarks>Gregory T. Moskoff became a reporting person of FactSet Research Systems Inc. (the&quot;Company&quot; or &quot;FactSet&quot;) pursuant to his appointment as the Company's Principal Accounting Officer on July 11, 2019.  Mr. Moskoff currently has no FactSet holdings.</remarks>

    <ownerSignature>
        <signatureName>/s/ Gregory T. Moskoff</signatureName>
        <signatureDate>2019-07-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
