FMR Reports 14.8% Stake in Allegro Microsystems

FMR LLC filed an Amendment No. 6 to a Schedule 13G/A reporting beneficial ownership of 27,421,205.61 shares of Allegro Microsystems Inc. common stock, equal to 14.8% of the class as of 03/31/2026.

Rhea-AI Filing Summary

FMR LLC filed an Amendment No. 6 to a Schedule 13G/A reporting beneficial ownership of 27,421,205.61 shares of Allegro Microsystems Inc. common stock, equal to 14.8% of the class as of 03/31/2026. The filing states FMR has sole dispositive power for 27,421,205.61 shares and sole voting power for 27,384,847.96 shares. The filing also discloses that the Select Semiconductors Portfolio held 16,576,021 shares (8.9%) as of 03/31/2026. Signatures indicate authorization under a power of attorney.

Insights

Governance Analyst

FMR reports a substantial passive stake in Allegro Microsystems (14.8% as of 03/31/2026).

The filing is a routine institutional disclosure under Schedule 13G/A showing beneficial ownership and voting/dispositive powers. It lists exact share counts and the Select Semiconductors Portfolio holding 16,576,021 shares.

Because Schedule 13G/A typically indicates passive intent, this is an ownership disclosure rather than an active control filing; subsequent filings would show any change in intent or control.

Institutional Ownership Specialist

Numbers provide clear ownership and power breakdown useful for shareholder cap-table analysis.

The report specifies sole voting and sole dispositive powers with precise share counts, helping to identify voting influence versus dispositive authority within FMR's structure.

Investors or governance teams tracking major holders can use these figures as a snapshot of institutional concentration as of 03/31/2026.

Key Figures

FMR beneficial ownership: 27,421,205.61 shares Percent of class: 14.8% Sole voting power: 27,384,847.96 shares +2 more

5 metrics

FMR beneficial ownership 27,421,205.61 shares as of 03/31/2026

Percent of class 14.8% ownership percentage as of 03/31/2026

Sole voting power 27,384,847.96 shares reported on cover page

Sole dispositive power 27,421,205.61 shares reported on cover page

Select Semiconductors Portfolio holding 16,576,021 shares 8.9% as of 03/31/2026

Key Terms

Schedule 13G/A, Beneficially owned, Sole dispositive power, Power of Attorney

4 terms

Schedule 13G/A regulatory

"Amendment No. 6 and cover references to beneficial ownership filing"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

Beneficially owned financial

"Item 4(a) Amount beneficially owned: 27421205.61"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Sole dispositive power regulatory

"Cover page: Sole Dispositive Power 27,421,205.61"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

Power of Attorney legal

"Signed: Duly authorized under Power of Attorney effective as of April 13, 2026"

A power of attorney is a legal document that allows one person to make decisions and act on behalf of another person, often in financial or legal matters. It’s like giving someone a trusted helper or agent the authority to handle important tasks if you are unable to do so yourself. This matters to investors because it can impact how their assets are managed or transferred if they become unable to oversee their affairs.

FAQ

What stake does FMR LLC report in ALGM?

FMR LLC reports beneficial ownership of 27,421,205.61 shares, representing 14.8% of Allegro Microsystems common stock as of 03/31/2026. The filing lists voting and dispositive power held by FMR.

What is the Select Semiconductors Portfolio holding in ALGM?

The Select Semiconductors Portfolio held 16,576,021 shares, equal to 8.9% of the outstanding common stock as of 03/31/2026. This holding is disclosed as part of FMR's aggregated interests.

Does the 13G/A indicate active control of Allegro Microsystems?

No; a Schedule 13G/A typically indicates an institutional, passive reporting stance. The filing shows ownership and voting/dispositive powers but does not assert control actions or intent to influence management.

Who signed the filing for FMR LLC and under what authority?

The filing was signed by Richard Bourgelas as duly authorized under a Power of Attorney effective April 13, 2026. Signatures reference an incorporated power of attorney exhibit previously filed.

What voting and dispositive powers does FMR report?

FMR reports sole voting power of 27,384,847.96 shares and sole dispositive power of 27,421,205.61 shares over Allegro Microsystems common stock as disclosed on the cover page.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 05/06/2026 - 11:00 AM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 6)

ALLEGRO MICROSYSTEMS INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

01749D105

(CUSIP Number)

03/31/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 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 27,384,847.96
6	Shared Voting Power 0.00
7	Sole Dispositive Power 27,421,205.61
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

27,421,205.61

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)

14.8 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP Number(s): 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 27,421,205.61
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

27,421,205.61

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)

14.8 %

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: 27421205.61
(b)	Percent of class: 14.8 %
(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: 27421205.61
	(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 16576021.00 shares or 8.9% of the total outstanding COMMON STOCK at 03/31/2026.
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:	Richard Bourgelas
Name/Title:	Duly authorized under Power of Attorney effective as of April 13, 2026, by and on behalf of FMR LLC and its direct and indirect subsidiaries*
Date:	05/05/2026

Abigail P. Johnson

Signature:	Richard Bourgelas
Name/Title:	Duly authorized under Power of Attorney effective as of April 13, 2026, by and on behalf of Abigail P. Johnson*
Date:	05/05/2026

Comments accompanying signature: *This power of attorney is incorporated herein by reference to Exhibit 24 to the Schedule 13G filed by FMR LLC on April 29,2026, accession number: 0000315066-26-000738.

Exhibit Information

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