Iron Mountain (IRM) director adds common shares via deferred plan

Rhea-AI Filing Summary

Iron Mountain Incorporated director Robin Matlock converted 10.189 Phantom Stock units into the same number of shares of Common Stock on January 21, 2026 under the company’s Directors Deferred Compensation Plan. The conversion price was reported as $0 per share, reflecting settlement of previously accrued phantom stock rather than an open‑market purchase. Following this transaction, Matlock directly beneficially owns 28,559.189 shares of Iron Mountain common stock.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Matlock Robin

(Last) (First) (Middle)

C/O IRON MOUNTAIN INCORPORATED

85 NEW HAMPSHIRE AVENUE, SUITE 150

(Street)

PORTSMOUTH NH 03801

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
IRON MOUNTAIN INC [ IRM ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
01/21/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock, par value $.01 per share	01/21/2026		M		10.189	A	$0	28,559.189	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Phantom Stock	(1)	01/21/2026		M			10.189(2)	(1)	(1)	Common Stock	10.189	$0	0	D

Explanation of Responses:

1. Pursuant to the Reporting Person's election to participate in the Iron Mountain Incorporated Directors Deferred Compensation Plan (the "Plan"), the shares of phantom stock (the "Phantom Shares") will become payable in shares of Iron Mountain Incorporated common stock ("Common Stock") on various dates selected by the Reporting Person or as otherwise provided in the Plan. Each Phantom Share is the economic equivalent of one share of Common Stock.

2. Settlement of the Phantom Shares is in Common Stock

Remarks:

	/s/ Christine Zhang, under Power of Attorney dated May 12, 2025 from Robin Matlock	01/22/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transaction did IRM director Robin Matlock report?

Director Robin Matlock reported a transaction coded M, converting 10.189 Phantom Stock units into 10.189 shares of Iron Mountain Common Stock on January 21, 2026.

How many Iron Mountain (IRM) shares does Robin Matlock own after this Form 4?

After the reported transaction, Robin Matlock directly beneficially owns 28,559.189 shares of Iron Mountain Incorporated common stock.

What is Phantom Stock in the context of IRM's director compensation?

Phantom Stock units are part of the Iron Mountain Directors Deferred Compensation Plan, where each unit is the economic equivalent of one share of Common Stock and becomes payable in shares on dates selected under the plan.

Was the IRM director’s Phantom Stock conversion an open-market purchase?

No. The $0 per share price and transaction code M indicate a settlement of Phantom Stock into Common Stock under the deferred compensation plan, not an open‑market trade.

How and when are IRM Phantom Stock units settled for directors?

According to the plan, Phantom Stock units become payable in Iron Mountain common stock on various dates selected by the reporting director or as otherwise provided in the Directors Deferred Compensation Plan.

Does the Form 4 indicate indirect ownership or a separate entity for this IRM transaction?

No. The filing shows the holdings as Direct (D) ownership with no separate nature of indirect beneficial ownership disclosed for this transaction.