<SEC-DOCUMENT>0001387467-15-000051.txt : 20150406
<SEC-HEADER>0001387467-15-000051.hdr.sgml : 20150406
<ACCEPTANCE-DATETIME>20150406160454
ACCESSION NUMBER:		0001387467-15-000051
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20150402
FILED AS OF DATE:		20150406
DATE AS OF CHANGE:		20150406

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ALPHA & OMEGA SEMICONDUCTOR Ltd
		CENTRAL INDEX KEY:			0001387467
		STANDARD INDUSTRIAL CLASSIFICATION:	SEMICONDUCTORS & RELATED DEVICES [3674]
		IRS NUMBER:				000000000

	BUSINESS ADDRESS:	
		STREET 1:		475 OAKMEAD PARKWAY
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94085
		BUSINESS PHONE:		408-830-9742

	MAIL ADDRESS:	
		STREET 1:		475 OAKMEAD PARKWAY
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94085

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ALPHA & OMEGA SEMICONDUCTOR LTD
		DATE OF NAME CHANGE:	20070123

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Grizelj Tony
		CENTRAL INDEX KEY:			0001540972

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34717
		FILM NUMBER:		15753690

	MAIL ADDRESS:	
		STREET 1:		475 OAKMEAD PARKWAY
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94085
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_142835068400697.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-04-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001387467</issuerCik>
        <issuerName>ALPHA &amp; OMEGA SEMICONDUCTOR Ltd</issuerName>
        <issuerTradingSymbol>AOSL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001540972</rptOwnerCik>
            <rptOwnerName>Grizelj Tony</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>475 OAKMEAD PKWY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SUNNYVALE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94085</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP of Power Discrete Product</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2015-04-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>32966</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2015-04-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4500</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.9209</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>28466</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Share Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-04-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-04-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4500.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes an aggregate of 25,174 shares subject to restricted stock unit awards which will be issued as such units vest in accordance with their terms.</footnote>
        <footnote id="F2">The sales were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on February 12, 2015.</footnote>
        <footnote id="F3">The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $8.85 to $9.13, inclusive. The Reporting Person undertakes to provide to Alpha and Omega Semiconductor Limited, any security holder of Alpha and Omega Semiconductor Limited, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within such range.</footnote>
        <footnote id="F4">The option is fully vested and immediately exercisable for all option shares.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Yanbing Hong, attorney-in-fact for Tony Grizelj</signatureName>
        <signatureDate>2015-04-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
