<SEC-DOCUMENT>0000315066-25-001445.txt : 20250512
<SEC-HEADER>0000315066-25-001445.hdr.sgml : 20250512
<ACCEPTANCE-DATETIME>20250512102440
ACCESSION NUMBER:		0000315066-25-001445
CONFORMED SUBMISSION TYPE:	SCHEDULE 13G/A
PUBLIC DOCUMENT COUNT:		2
FILED AS OF DATE:		20250512
DATE AS OF CHANGE:		20250512

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ALLEGRO MICROSYSTEMS, INC.
		CENTRAL INDEX KEY:			0000866291
		STANDARD INDUSTRIAL CLASSIFICATION:	SEMICONDUCTORS & RELATED DEVICES [3674]
		ORGANIZATION NAME:           	04 Manufacturing
		EIN:				462405937
		FISCAL YEAR END:			0331

	FILING VALUES:
		FORM TYPE:		SCHEDULE 13G/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-92108
		FILM NUMBER:		25933156

	BUSINESS ADDRESS:	
		STREET 1:		955 PERIMETER ROAD
		CITY:			MANCHESTER
		STATE:			NH
		ZIP:			03103
		BUSINESS PHONE:		(603) 626-2300

	MAIL ADDRESS:	
		STREET 1:		955 PERIMETER ROAD
		CITY:			MANCHESTER
		STATE:			NH
		ZIP:			03103

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ALLEGRO MICROSYSTEMS INC
		DATE OF NAME CHANGE:	19900730

FILED BY:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FMR LLC
		CENTRAL INDEX KEY:			0000315066
		STANDARD INDUSTRIAL CLASSIFICATION:	UNKNOWN SIC - 0000 [0000]
		ORGANIZATION NAME:           	
		EIN:				043532603
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SCHEDULE 13G/A

	BUSINESS ADDRESS:	
		STREET 1:		245 SUMMER STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02210
		BUSINESS PHONE:		6175706339

	MAIL ADDRESS:	
		STREET 1:		245 SUMMER STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02210

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	FMR CORP
		DATE OF NAME CHANGE:	19920717
</SEC-HEADER>
<DOCUMENT>
<TYPE>SCHEDULE 13G/A
<SEQUENCE>1
<FILENAME>primary_doc.xml
<TEXT>
<XML>
<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/schedule13g" xmlns:com="http://www.sec.gov/edgar/common">
 <headerData>
  <submissionType>SCHEDULE 13G/A</submissionType>
  <previousAccessionNumber>0000315066-24-001002</previousAccessionNumber>
  <filerInfo>
   <filer>
    <filerCredentials>
     <cik>0000315066</cik>
     <ccc>XXXXXXXX</ccc>
    </filerCredentials>
   </filer>
   <liveTestFlag>LIVE</liveTestFlag>


  </filerInfo>
 </headerData>
 <formData>
  <coverPageHeader>
   <amendmentNo>4</amendmentNo>
   <securitiesClassTitle>COMMON STOCK</securitiesClassTitle>
   <eventDateRequiresFilingThisStatement>03/31/2025</eventDateRequiresFilingThisStatement>
   <issuerInfo>
    <issuerCik>0000866291</issuerCik>
    <issuerName>ALLEGRO MICROSYSTEMS INC</issuerName>
    <issuerCusip>01749D105</issuerCusip>
    <issuerPrincipalExecutiveOfficeAddress>
     <com:street1>955 PERIMETER ROAD</com:street1>
     <com:city>MANCHESTER</com:city>
     <com:stateOrCountry>NH</com:stateOrCountry>
     <com:zipCode>03103</com:zipCode>
    </issuerPrincipalExecutiveOfficeAddress>
   </issuerInfo>
   <designateRulesPursuantThisScheduleFiled>
    <designateRulePursuantThisScheduleFiled>Rule 13d-1(b)</designateRulePursuantThisScheduleFiled>
   </designateRulesPursuantThisScheduleFiled>
  </coverPageHeader>
  <coverPageHeaderReportingPersonDetails>

   <reportingPersonName>FMR LLC</reportingPersonName>
   <citizenshipOrOrganization>DE</citizenshipOrOrganization>
   <reportingPersonBeneficiallyOwnedNumberOfShares>
    <soleVotingPower>26476963.11</soleVotingPower>
    <sharedVotingPower>0.00</sharedVotingPower>
    <soleDispositivePower>26921116.28</soleDispositivePower>
    <sharedDispositivePower>0.00</sharedDispositivePower>
   </reportingPersonBeneficiallyOwnedNumberOfShares>
   <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>26921116.28</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
   <classPercent>14.6</classPercent>
   <typeOfReportingPerson>HC</typeOfReportingPerson>
  </coverPageHeaderReportingPersonDetails>
  <coverPageHeaderReportingPersonDetails>
   <reportingPersonName>Abigail P. Johnson</reportingPersonName>
   <citizenshipOrOrganization>X1</citizenshipOrOrganization>
   <reportingPersonBeneficiallyOwnedNumberOfShares>
    <soleVotingPower>0.00</soleVotingPower>
    <sharedVotingPower>0.00</sharedVotingPower>
    <soleDispositivePower>26921116.28</soleDispositivePower>
    <sharedDispositivePower>0.00</sharedDispositivePower>
   </reportingPersonBeneficiallyOwnedNumberOfShares>
   <reportingPersonBeneficiallyOwnedAggregateNumberOfShares>26921116.28</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
   <classPercent>14.6</classPercent>
   <typeOfReportingPerson>IN</typeOfReportingPerson>
  </coverPageHeaderReportingPersonDetails>
  <items>
   <item1>
    <issuerName>ALLEGRO MICROSYSTEMS INC</issuerName>
    <issuerPrincipalExecutiveOfficeAddress>955 PERIMETER ROAD,MANCHESTER,NH,USA,03103</issuerPrincipalExecutiveOfficeAddress>
   </item1>
   <item2>
    <filingPersonName>FMR LLC</filingPersonName>
    <principalBusinessOfficeOrResidenceAddress>245 Summer Street, Boston, Massachusetts 02210</principalBusinessOfficeOrResidenceAddress>
    <citizenship>Not applicable</citizenship>
   </item2>
   <item3>
    <notApplicableFlag>N</notApplicableFlag>
    <typeOfPersonFiling>HC</typeOfPersonFiling>
   </item3>
   <item4>
    <amountBeneficiallyOwned>26921116.28</amountBeneficiallyOwned>
    <classPercent>14.6</classPercent>
    <numberOfSharesPersonHas>
     <solePowerOrDirectToVote>Please see the responses to Items 5 and 6 on the cover page.</solePowerOrDirectToVote>
     <sharedPowerOrDirectToVote>0.00</sharedPowerOrDirectToVote>
     <solePowerOrDirectToDispose>26921116.28</solePowerOrDirectToDispose>
     <sharedPowerOrDirectToDispose>0.00</sharedPowerOrDirectToDispose>
    </numberOfSharesPersonHas>
   </item4>
   <item5>
    <notApplicableFlag>Y</notApplicableFlag>
    <classOwnership5PercentOrLess>N</classOwnership5PercentOrLess>
   </item5>
   <item6>
    <notApplicableFlag>N</notApplicableFlag>
    <ownershipMoreThan5PercentOnBehalfOfAnotherPerson>One or more other persons are known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the COMMON STOCK of ALLEGRO MICROSYSTEMS INC. The interest of Select Semiconductors Portfolio, in the COMMON STOCK of ALLEGRO MICROSYSTEMS INC, amounted to 12657997.00 shares or 6.9% of the total outstanding COMMON STOCK at 03/31/2025.</ownershipMoreThan5PercentOnBehalfOfAnotherPerson>
   </item6>
   <item7>
    <notApplicableFlag>N</notApplicableFlag>
    <subsidiaryIdentificationAndClassification>See attached Exhibit 99.</subsidiaryIdentificationAndClassification>
   </item7>
   <item8>
    <notApplicableFlag>Y</notApplicableFlag>
   </item8>
   <item9>
    <notApplicableFlag>Y</notApplicableFlag>
   </item9>
   <item10>
    <notApplicableFlag>N</notApplicableFlag>
    <certifications>By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.</certifications>
   </item10>
  </items>
  <exhibitInfo>Please see Exhibit 99 for 13d-1(k) (1) agreement.</exhibitInfo>
  <signatureInformation>
   <reportingPersonName>FMR LLC</reportingPersonName>
   <signatureDetails>
    <signature>Stephanie J. Brown</signature>
    <title>Duly authorized under Power of Attorney effective as of January 3, 2023, by and on behalf of FMR LLC and its direct and indirect subsidiaries*</title>
    <date>05/09/2025</date>
   </signatureDetails>
  </signatureInformation>
  <signatureInformation>
   <reportingPersonName>Abigail P. Johnson</reportingPersonName>
   <signatureDetails>
    <signature>Stephanie J. Brown</signature>
    <title>Duly authorized under Power of Attorney effective as of January 26, 2023, by and on behalf of Abigail P. Johnson**</title>
    <date>05/09/2025</date>
   </signatureDetails>
  </signatureInformation>
  <signatureComments>* This power of attorney is incorporated herein by reference to Exhibit 24 to the Schedule 13G filed by FMR LLC on January 10, 2023, accession number: 0000315066-23-000003.** This power of attorney is incorporated herein by reference to Exhibit 24 to the Schedule 13G filed by FMR LLC on January 31, 2023, accession number: 0000315066-23-000038.</signatureComments>
 </formData>

</edgarSubmission>
</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-99
<SEQUENCE>2
<FILENAME>exhibit99.txt
<TEXT>

Exhibit 99


Pursuant to the instructions in Item 7 of Schedule 13G, the following table
lists the identity and Item 3 classification, if applicable, of each relevant
entity that beneficially owns shares of the security class being reported on
this Schedule 13G.

Entity   ITEM 3 Classification

FIAM LLC  IA
Fidelity Institutional Asset Management Trust Company  BK
Fidelity Management & Research Company LLC * IA
Fidelity Management Trust Company  BK
Strategic Advisers LLC  IA



* Entity beneficially owns 5% or greater of the outstanding shares of the
security class being reported on this Schedule 13G.


Abigail P. Johnson is a Director, the Chairman and the Chief Executive Officer
of FMR LLC.

Members of the Johnson family, including Abigail P. Johnson, are the
predominant owners, directly or through trusts, of Series B voting common
shares of FMR LLC, representing 49% of the voting power of FMR LLC. The
Johnson family group and all other Series B shareholders have entered into a
shareholders' voting agreement under which all Series B voting common shares
will be voted in accordance with the majority vote of Series B voting common
shares. Accordingly, through their ownership of voting common shares and the
execution of the shareholders' voting agreement, members of the Johnson family
may be deemed, under the Investment Company Act of 1940, to form a controlling
group with respect to FMR LLC.

This filing reflects the securities beneficially owned, or that may be deemed
to be beneficially owned, by FMR LLC, certain of its subsidiaries and
affiliates, and other companies (collectively, the "FMR Reporters"). This
filing does not reflect securities, if any, beneficially owned by certain
other companies whose beneficial ownership of securities is disaggregated from
that of the FMR Reporters in accordance with Securities and Exchange
Commission Release No. 34-39538 (January 12, 1998).


RULE 13d-1(k)(1) AGREEMENT

The undersigned persons, on May 9, 2025, agree and consent to the joint filing
on their behalf of this Schedule 13G in connection with their beneficial
ownership of the COMMON STOCK of ALLEGRO MICROSYSTEMS INC at March 31, 2025.

FMR LLC

By /s/ Stephanie J. Brown
Stephanie J. Brown
Duly authorized under Power of Attorney effective as of January 3, 2023, by
and on behalf of FMR LLC and its direct and indirect subsidiaries*

Abigail P. Johnson

By /s/ Stephanie J. Brown
Stephanie J. Brown
Duly authorized under Power of Attorney effective as of January 26, 2023, by
and on behalf of Abigail P. Johnson**


* This power of attorney is incorporated herein by reference to Exhibit 24 to
the Schedule 13G filed by FMR LLC on January 10, 2023, accession number:
0000315066-23-000003.

** This power of attorney is incorporated herein by reference to Exhibit 24 to
the Schedule 13G filed by FMR LLC on January 31, 2023, accession number:
0000315066-23-000038.


</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
