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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2025-05-28</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001492422</issuerCik>
        <issuerName>Apellis Pharmaceuticals, Inc.</issuerName>
        <issuerTradingSymbol>APLS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002070437</rptOwnerCik>
            <rptOwnerName>Boucher Kelley</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O APELLIS PHARMACEUTICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>100 FIFTH AVENUE, 3RD FLOOR</rptOwnerStreet2>
            <rptOwnerCity>WALTHAM</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02451</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Chief People Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <footnotes></footnotes>

    <ownerSignature>
        <signatureName>/s/ David Watson, attorney-in-fact for Kelley Boucher</signatureName>
        <signatureDate>2025-05-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
