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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-01-26</periodOfReport>

    <issuer>
        <issuerCik>0001596993</issuerCik>
        <issuerName>DORIAN LPG LTD.</issuerName>
        <issuerTradingSymbol>LPG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001649312</rptOwnerCik>
            <rptOwnerName>BW Group Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MAPLETREE BUSINESS CITY, #18-01;</rptOwnerStreet1>
            <rptOwnerStreet2>10 PASIR PANJANG ROAD</rptOwnerStreet2>
            <rptOwnerCity>SINGAPORE</rptOwnerCity>
            <rptOwnerState>U0</rptOwnerState>
            <rptOwnerZipCode>117438</rptOwnerZipCode>
            <rptOwnerStateDescription>SINGAPORE</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isTenPercentOwner>true</isTenPercentOwner>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001649311</rptOwnerCik>
            <rptOwnerName>BW Euroholdings Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MAPLETREE BUSINESS CITY, #18-01;</rptOwnerStreet1>
            <rptOwnerStreet2>10 PASIR PANJANG ROAD</rptOwnerStreet2>
            <rptOwnerCity>SINGAPORE</rptOwnerCity>
            <rptOwnerState>U0</rptOwnerState>
            <rptOwnerZipCode>117438</rptOwnerZipCode>
            <rptOwnerStateDescription>SINGAPORE</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isTenPercentOwner>true</isTenPercentOwner>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001373176</rptOwnerCik>
            <rptOwnerName>Sohmen Family Foundation</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>HEILIGKREUZ 6, P O BOX 484</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>VADUZ</rptOwnerCity>
            <rptOwnerState>N2</rptOwnerState>
            <rptOwnerZipCode>FL-9490</rptOwnerZipCode>
            <rptOwnerStateDescription>LIECHTENSTEIN</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isTenPercentOwner>true</isTenPercentOwner>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2018-01-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1100000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7.3</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7100000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2018-01-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>281460</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7.5</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7381460</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2018-01-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>445000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7.55</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7826460</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These shares are held directly by BW Euroholdings Limited, a wholly-owned subsidiary of BW Group Ltd.  The Sohmen Family Foundation holds 93.25% of BW Group Ltd.  Each reporting person disclaims beneficial ownership of the shares reported herein except to the extent of its pecuniary interest therein, and this report shall not be deemed an admission that such reporting person is the beneficial owner of the shares for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>BW GROUP LIMITED By: /s/ Nicholas Fell, Authorized Signatory</signatureName>
        <signatureDate>2018-01-29</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BW EUROHOLDINGS LIMITED By: /s/ Nicholas Fell, Authorized Signatory</signatureName>
        <signatureDate>2018-01-29</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>SOHMEN FAMILY FOUNDATION By: /s/Andreas Sohmen-Pao, Authorized Signatory</signatureName>
        <signatureDate>2018-01-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
