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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2017-05-04</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001326190</issuerCik>
        <issuerName>Altimmune, Inc.</issuerName>
        <issuerTradingSymbol>NASDAQ:ALT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001705562</rptOwnerCik>
            <rptOwnerName>Hodges Philip</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ALTIMMUNE INC.,</rptOwnerStreet1>
            <rptOwnerStreet2>19 FIRSTFIELD ROAD, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>GAITHERSBURG</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20878</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001705638</rptOwnerCik>
            <rptOwnerName>Redmont VAXN Capital Holdings, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ALTIMMUNE INC.,</rptOwnerStreet1>
            <rptOwnerStreet2>19 FIRSTFIELD ROAD, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>GAITHERSBURG</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20878</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001705640</rptOwnerCik>
            <rptOwnerName>Paradigm Venture Partners, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ALTIMMUNE INC.,</rptOwnerStreet1>
            <rptOwnerStreet2>19 FIRSTFIELD ROAD, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>GAITHERSBURG</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20878</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001705639</rptOwnerCik>
            <rptOwnerName>Redmont Venture Partners, Inc.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ALTIMMUNE INC.,</rptOwnerStreet1>
            <rptOwnerStreet2>19 FIRSTFIELD ROAD, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>GAITHERSBURG</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20878</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <footnotes></footnotes>

    <remarks>Exhibit 24.1 - Power of Attorney</remarks>

    <ownerSignature>
        <signatureName>/s/ Ori Solomon, Attorney in fact for Philip Hodges</signatureName>
        <signatureDate>2017-05-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Ori Solomon, Attorney in fact for Redmont VAXN Capital Holdings, LLC</signatureName>
        <signatureDate>2017-05-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Ori Solomon, Attorney in fact for Redmont Venture Partners, Inc.</signatureName>
        <signatureDate>2017-05-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Ori Solomon, Attorney in fact for Paradigm Venture Partners, L.P.</signatureName>
        <signatureDate>2017-05-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
