[SCHEDULE 13G] IRON MOUNTAIN INC SEC Filing

Rhea-AI Filing Summary

Cohen & Steers and affiliates filed a Schedule 13G reporting a significant stake in Iron Mountain (IRM). The group reported beneficial ownership of 16,029,962 shares of common stock, representing 5.43% of the class as of the event date 09/30/2025. They reported sole voting power over 12,328,467 shares and sole dispositive power over 16,029,962 shares, with no shared voting or dispositive power. Subsidiaries hold the securities for the benefit of account holders, who may receive dividends or sale proceeds.

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)

09/30/2025

(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. 46284V101

1

Names of Reporting Persons

Cohen & Steers, Inc.

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 12,328,467.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 16,029,962.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

16,029,962.00

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)

5.43 %

12

Type of Reporting Person (See Instructions)

HC, CO

SCHEDULE 13G

CUSIP No. 46284V101

1

Names of Reporting Persons

Cohen & Steers Capital Management, Inc.

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

NEW YORK

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 12,243,203.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 15,841,858.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

15,841,858.00

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)

5.36 %

12

Type of Reporting Person (See Instructions)

IA, CO

SCHEDULE 13G

CUSIP No. 46284V101

1

Names of Reporting Persons

Cohen & Steers UK Limited

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 KINGDOM

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 68,948.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 171,788.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

171,788.00

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)

0.06 %

12

Type of Reporting Person (See Instructions)

IA, CO

SCHEDULE 13G

CUSIP No. 46284V101

1

Names of Reporting Persons

Cohen & Steers Asia Limited

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

HONG KONG

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 0.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

0.00

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)

0.00 %

12

Type of Reporting Person (See Instructions)

IA, CO

SCHEDULE 13G

CUSIP No. 46284V101

1

Names of Reporting Persons

Cohen & Steers Ireland Limited

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

IRELAND

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 16,316.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 16,316.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

16,316.00

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)

0.01 %

12

Type of Reporting Person (See Instructions)

FI, CO

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Iron Mountain, Inc.
(b)	Address of issuer's principal executive offices: 85 New Hampshire Avenue, Suite 150 Portsmouth, NH 03801 USA
Item 2.
(a)	Name of person filing: Cohen & Steers, Inc. Cohen & Steers Capital Management, Inc. Cohen & Steers UK Ltd Cohen & Steers Asia Ltd Cohen & Steers Ireland Ltd
(b)	Address or principal business office or, if none, residence: The principal address for Cohen & Steers, Inc. and Cohen & Steers Capital Management, Inc. is: 1166 Avenue of the Americas, 30th Floor New York, NY 10036 The principal address for Cohen & Steers UK Ltd. is: The Burlian, 2nd Floor 3 Dering Street, London W1S 1AA United Kingdom The principal address for Cohen & Steers Asia Ltd. is: 3301B, 33rd Floor, The Henderson 2 Murray Road Central, Hong Kong The principal address for Cohen & Steers Ireland Ltd. is: Suite G01 81 Merrion Square South Dublin 2 D02 NR12 Ireland
(c)	Citizenship: Cohen & Steers, Inc: Delaware corporation Cohen & Steers Capital Management, Inc: New York corporation Cohen & Steers UK Ltd: United Kingdom Private Limited Company Cohen & Steers Asia Ltd: Asia Private Limited Company Cohen & Steers Ireland Ltd: Ireland Private Limited Company
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 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).
	Corporation
Item 4.	Ownership
(a)	Amount beneficially owned: 16,029,962
(b)	Percent of class: 5.43%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 12,328,467
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 16,029,962
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
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. Each of Cohen & Steers Capital Management, Inc., Cohen & Steers UK Ltd., Cohen & Steers Asia Ltd. and Cohen & Steers Ireland Ltd. holds the securities of the Issuer to which this statement relates for the benefit of their respective account holders. Such account holders have the right to receive or the power to direct the receipt of dividends from, or proceeds from the sale of, the securities of the Issuer that are held on their behalf.
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. Cohen & Steers, Inc. holds a 100% interest in Cohen & Steers Capital Management, Inc., Cohen & Steers UK Ltd., Cohen & Steers Asia Ltd. (investment advisors registered under Section 203 of the Investment Advisers Act) and Cohen & Steers Ireland Ltd. (a non-US institution).
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.

Cohen & Steers, Inc.

Signature:	/s/ Nargis Hilal
Name/Title:	SVP, Global Chief Compliance Officer & Associate General Counsel
Date:	11/14/2025

Cohen & Steers Capital Management, Inc.

Signature:	/s/ Nargis Hilal
Name/Title:	SVP, Global Chief Compliance Officer & Associate General Counsel
Date:	11/14/2025

Cohen & Steers UK Limited

Signature:	/s/ Nargis Hilal
Name/Title:	SVP, Global Chief Compliance Officer & Associate General Counsel
Date:	11/14/2025

Cohen & Steers Asia Limited

Signature:	/s/ Catherine Cheng
Name/Title:	VP, Compliance Officer
Date:	11/14/2025

Cohen & Steers Ireland Limited

Signature:	/s/ Alan Cooper
Name/Title:	VP, Compliance Officer
Date:	11/14/2025

FAQ

What stake in IRM did Cohen & Steers report?

They reported beneficial ownership of 16,029,962 Iron Mountain shares, equal to 5.43% of the class.

What voting power did the filer report over IRM shares?

They reported 12,328,467 shares with sole voting power and 0 shared voting power.

What dispositive power did the filer report?

They reported 16,029,962 shares with sole dispositive power and 0 shared dispositive power.

Which entities filed the 13G for IRM?

The filing names Cohen & Steers, Inc. and affiliates including Cohen & Steers Capital Management, Inc., UK Ltd, Asia Ltd, and Ireland Ltd.

What is the date of the event requiring the filing?

The Schedule 13G lists the event date as 09/30/2025.

Are the IRM shares held for clients?

Yes. The subsidiaries hold the securities for the benefit of their account holders, who may receive dividends or sale proceeds.

Under which rule is the 13G filed?

The cover indicates the filing is pursuant to Rule 13d‑1(b)/(c)/(d), consistent with a passive ownership report.