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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2022-01-05</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001800315</issuerCik>
        <issuerName>Galecto, Inc.</issuerName>
        <issuerTradingSymbol>GLTO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001901450</rptOwnerCik>
            <rptOwnerName>Oestreich Stephanie</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O GALECTO, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>OLE MAALOES VEJ 3</rptOwnerStreet2>
            <rptOwnerCity>OLE MAALOES VEJ 3</rptOwnerCity>
            <rptOwnerState>G7</rptOwnerState>
            <rptOwnerZipCode>DK-2200</rptOwnerZipCode>
            <rptOwnerStateDescription>DENMARK</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Business Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <footnotes></footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Garrett Winslow, Attorney-in-fact</signatureName>
        <signatureDate>2022-01-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
