X0609 4 2026-10-02 0 0001020569 IRON MOUNTAIN INC IRM 0001688276 Samuels Theodore R. II false C/O IRON MOUNTAIN INCORPORATED 85 NEW HAMPSHIRE AVENUE, SUITE 150 PORTSMOUTH NH 03801 1 0 0 0 0 Phantom Stock 2026-10-02 4 A 0 104.67 113.92 A Common Stock 104.67 13905 D Pursuant to the Reporting Person's election to participate in the Iron Mountain Incorporated Directors Deferred Compensation Plan, the shares of phantom stock (the "Phantom Shares") will become payable in shares of Iron Mountain Incorporated common stock ("Common Stock") following the Reporting Person's disability or cessation of service as a director. Each Phantom Share is the economic equivalent of one share of Common Stock. These shares give effect to the Reporting Person's quarterly cash compensation for services on the board of directors of the Company as if reinvested in Phantom Shares. /s/ Keely Stewart, under Power of Attorney dated July 6, 2023 from Theodore R Samuels 2026-10-05