Vanguard reports 21.87M shares (7.35%) of Iron Mountain

Iron Mountain Inc ownership filing shows Vanguard Capital Management reports beneficial ownership of 21,872,303 shares of Common Stock, representing 7.35% of the class.

Rhea-AI Filing Summary

Iron Mountain Inc ownership filing shows Vanguard Capital Management reports beneficial ownership of 21,872,303 shares of Common Stock, representing 7.35% of the class. The filing states Vanguard has sole dispositive power over 21,872,303 shares and sole voting power over 3,113,414 shares. The schedule notes these holdings include securities managed for Vanguard funds and affiliated business divisions and that Vanguard entities have the right to receive dividends or proceeds on behalf of managed accounts.

Insights

Institutional Ownership Analyst

Vanguard reports a 7.35% passive stake in Iron Mountain (21,872,303 shares).

Vanguard Capital Management discloses beneficial ownership of 21,872,303 shares with sole dispositive power over the same amount and sole voting power over 3,113,414 shares. The filing is a standard Schedule 13G disclosure for large passive holders.

Holder decisions, proxy voting by affiliated divisions, and fund flows could influence future disclosures. Subsequent filings may report changes in the percentage or voting/dispositive breakdown.

Key Figures

Beneficial ownership: 21,872,303 shares Percent of class: 7.35% Sole voting power: 3,113,414 shares +1 more

4 metrics

Beneficial ownership 21,872,303 shares Amount beneficially owned as reported

Percent of class 7.35% Percent of class as reported

Sole voting power 3,113,414 shares Sole power to vote or to direct the vote

Sole dispositive power 21,872,303 shares Sole power to dispose or to direct the disposition

Key Terms

Schedule 13G, beneficially owned, sole dispositive power

3 terms

Schedule 13G regulatory

"reports beneficial ownership of 21,872,303 shares"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

beneficially owned financial

"Amount beneficially owned: 21872303"

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

"Sole power to dispose or to direct the disposition of: 21872303"

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.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What stake does Vanguard Capital Management report in Iron Mountain (IRM)?

Vanguard reports beneficial ownership of 21,872,303 shares (7.35%). The schedule states Vanguard has sole dispositive power over these shares and sole voting power over 3,113,414 shares as reported on 03/31/2026.

Does Vanguard control voting for all reported IRM shares?

No — Vanguard reports sole voting power for 3,113,414 shares. The filing shows sole dispositive power for 21,872,303 shares but only 3,113,414 shares with sole voting power; shared voting/dispositive power are reported as zero.

Are the IRM shares held on behalf of Vanguard funds or clients?

Yes — the filing states holdings include securities held by Vanguard funds and managed accounts. It lists affiliated business divisions that exercise dispositive or voting power over some of these securities on behalf of clients.

Does any single other person have more than 5% ownership of IRM in this filing?

No single other person's interest exceeds 5%. The filing states no one other person's interest in the reported securities is more than 5% of the class.

Who signed the Schedule 13G for Vanguard Capital Management?

The filing is signed by Ashley Grim, Head of Global Fund Administration. The signature block shows the filing date as 04/30/2026.

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

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Accepted by SEC EDGAR 04/30/2026 - 11:13 AM EDT Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Iron Mountain Inc

(Name of Issuer)

Common Stock

(Title of Class of Securities)

46284V101

(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): 46284V101

1

Names of Reporting Persons

Vanguard Capital Management

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

PENNSYLVANIA

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 3,113,414.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 21,872,303.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

21,872,303.00

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)

7.35 %

12

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person: In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by Vanguard Capital Management LLC and the following affiliates of Vanguard Capital Management LLC or business divisions of such affiliates: Vanguard Asset Management Limited, Vanguard Fiduciary Trust Company, Vanguard Global Advisers, LLC and Vanguard Investments Australia Ltd. This Schedule 13G includes securities held by Vanguard funds, or sleeves thereof, over which Vanguard Capital Management LLC exercises dispositive power, in addition to securities held by clients over which the affiliates or business divisions of such affiliates indicated above exercise dispositive and/or voting power. This Schedule 13G does not include securities, if any, beneficially owned by other subsidiaries or affiliates of Vanguard Capital Management LLC, or business divisions of such subsidiaries, whose ownership of securities is disaggregated from that of the reporting business unit in accordance with such release.

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Iron Mountain Inc
(b)	Address of issuer's principal executive offices: 1 Federal Street, Boston, MA, 02110
Item 2.
(a)	Name of person filing: Vanguard Capital Management
(b)	Address or principal business office or, if none, residence: 100 Vanguard Blvd,, Malvern, PA, 19355
(c)	Citizenship: PA
(d)	Title of class of securities: Common Stock
(e)	CUSIP Number(s): 46284V101
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: 21872303
(b)	Percent of class: 7.35 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 3113414
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 21872303
	(iv) Shared power to dispose or to direct the disposition of: 0
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. Vanguard Capital Management, including investment companies registered under the Investment Company Act of 1940 and other managed accounts, have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the securities reported herein.No one other person's interest in the securities reported herein is more than 5%.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
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.

Vanguard Capital Management

Signature:	Ashley Grim
Name/Title:	Head of Global Fund Administration
Date:	04/30/2026