FMR’s 12.8% Allegro MicroSystems (ALGM) stake detailed in Schedule 13G/A

Rhea-AI Filing Summary

FMR LLC and Abigail P. Johnson report significant passive ownership in Allegro MicroSystems, Inc. common stock. As of 12/31/2025, they beneficially owned 23,635,746.28 shares, representing 12.8% of the outstanding common stock.

The filing notes that one or more other persons have rights to dividends or sale proceeds, including Select Semiconductors Portfolio, whose interest amounted to 14,179,921.00 Allegro shares, or 7.7% of the total outstanding common stock at 12/31/2025. The holders certify the position is held in the ordinary course of business and not for the purpose of changing or influencing control of Allegro.

Insights

Institutional ownership and governance analyst

FMR reports a 12.8% passive stake in Allegro MicroSystems.

FMR LLC and Abigail P. Johnson disclose beneficial ownership of 23,635,746.28 Allegro MicroSystems common shares, equal to 12.8% of the class as of 12/31/2025. This positions FMR as a major institutional holder with notable influence on the shareholder base.

The filing highlights that Select Semiconductors Portfolio holds 14,179,921.00 Allegro shares, or 7.7% of outstanding stock at 12/31/2025, within the broader FMR complex. The certification states the stake is held in the ordinary course of business and not to change or influence control, aligning with a passive investment posture under Schedule 13G rules.

For investors, this document clarifies that a large, sophisticated asset manager has a sizable passive position in Allegro. Future ownership updates in subsequent beneficial-ownership filings may show whether FMR’s percentage stake increases, decreases, or remains stable over time.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 5)

ALLEGRO MICROSYSTEMS INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

01749D105

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 01749D105

1

Names of Reporting Persons

FMR LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 23,593,310.18
6	Shared Voting Power 0.00
7	Sole Dispositive Power 23,635,746.28
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

23,635,746.28

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

12.8 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP No. 01749D105

1

Names of Reporting Persons

Abigail P. Johnson

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 23,635,746.28
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

23,635,746.28

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

12.8 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: ALLEGRO MICROSYSTEMS INC
(b)	Address of issuer's principal executive offices: 955 PERIMETER ROAD,MANCHESTER,NH,USA,03103
Item 2.
(a)	Name of person filing: FMR LLC
(b)	Address or principal business office or, if none, residence: 245 Summer Street, Boston, Massachusetts 02210
(c)	Citizenship: Not applicable
(d)	Title of class of securities: COMMON STOCK
(e)	CUSIP No.: 01749D105
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 23635746.28
(b)	Percent of class: 12.8 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Please see the responses to Items 5 and 6 on the cover page.
	(ii) Shared power to vote or to direct the vote: 0.00
	(iii) Sole power to dispose or to direct the disposition of: 23635746.28
	(iv) Shared power to dispose or to direct the disposition of: 0.00
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. 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 14179921.00 shares or 7.7% of the total outstanding COMMON STOCK at 12/31/2025.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. See attached Exhibit 99.
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

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.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

FMR LLC

Signature:	Stephanie J. Brown
Name/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*
Date:	02/04/2026

Abigail P. Johnson

Signature:	Stephanie J. Brown
Name/Title:	Duly authorized under Power of Attorney effective as of January 26, 2023, by and on behalf of Abigail P. Johnson**
Date:	02/04/2026

Comments accompanying signature: * 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.

Exhibit Information

Please see Exhibit 99 for 13d-1(k) (1) agreement.

FAQ

How many Allegro MicroSystems (ALGM) shares does FMR LLC beneficially own?

FMR LLC reports beneficial ownership of 23,635,746.28 Allegro MicroSystems common shares. This stake represents 12.8% of Allegro’s outstanding common stock as of December 31, 2025, making FMR a major institutional holder in the company’s shareholder base.

What percentage of Allegro MicroSystems (ALGM) does FMR LLC’s stake represent?

FMR LLC’s beneficial ownership equals 12.8% of Allegro MicroSystems’ common stock. This percentage is based on 23,635,746.28 shares held as of December 31, 2025, and reflects FMR’s role as a significant, but passive, institutional shareholder in ALGM.

Who is identified as a major underlying holder within FMR’s Allegro (ALGM) position?

Select Semiconductors Portfolio is identified as a major underlying holder within FMR’s Allegro stake. It held 14,179,921.00 Allegro common shares, equal to 7.7% of the total outstanding stock at December 31, 2025, indicating concentrated exposure through that portfolio.

Is FMR LLC’s Allegro MicroSystems (ALGM) stake considered passive or activist?

FMR LLC characterizes its Allegro stake as passive. The certification states the securities were acquired and are held in the ordinary course of business, not for changing or influencing control of Allegro, consistent with a Schedule 13G rather than activist 13D posture.

What role does Abigail P. Johnson have in the Allegro MicroSystems (ALGM) filing?

Abigail P. Johnson is listed as a reporting person with sole dispositive power over 23,635,746.28 Allegro shares. The filing shows she shares beneficial ownership of the same 23,635,746.28 shares, representing 12.8% of the class, and signs through an authorized attorney-in-fact.

What does the Schedule 13G/A for Allegro MicroSystems (ALGM) certify about control intentions?

The Schedule 13G/A certifies that the Allegro shares were acquired and are held in the ordinary course of business. It further states they were not acquired and are not held to change or influence control of Allegro or as part of any such transaction.