Iron Mountain Incorporated
US ˙ NYSE ˙ US46284V1017

SecurityIRM / Iron Mountain Incorporated
InstitutionMorgan Stanley
Latest Disclosed Ownership4,652,247 shares
Latest Disclosed Value $ 475,180,655
Morgan Stanley reports 29.27% increase in ownership of IRM / Iron Mountain Incorporated

On May 15, 2026 - Morgan Stanley filed a 13F-HR form disclosing ownership of 4,652,247 shares of Iron Mountain Incorporated (US:IRM) valued at $475,180,509 USD as of March 31, 2026. The entity filed a previous 13F-HR/A on May 27, 2026 disclosing 3,598,973 shares of Iron Mountain Incorporated. This represents a change in shares of 29.27% during the quarter. The current value of the position is $595,255,004 USD.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F IRON MTN INC DEL COM 46284V101 4,652,247 1,053,274 29.27 475,181 59.17 0.0286
2026-05-27 2025-12-31 13F/A-1 IRON MTN INC DEL COM 46284V101 3,598,973 -12,426 -0.34 298,535 -18.91 0.0178
2026-02-13 2025-12-31 13F IRON MTN INC DEL COM 46284V101 3,598,973 -12,426 298,535 0.0178
2026-05-27 2025-09-30 13F/A-1 IRON MTN INC DEL COM 46284V101 3,611,399 104,916 2.99 368,146 2.36 0.0223
2025-11-14 2025-09-30 13F IRON MTN INC DEL COM 46284V101 3,611,399 104,916 368,146 0.0223
2025-08-15 2025-06-30 13F IRON MTN INC DEL COM 46284V101 3,506,483 117,444 3.47 359,660 23.34 0.0234
2025-05-15 2025-03-31 13F IRON MTN INC DEL COM 46284V101 3,389,039 2,824 0.08 291,593 -18.07 0.0208
2025-05-15 2024-12-31 13F/A-1 IRON MTN INC DEL COM 46284V101 3,386,215 -254,699 -7.00 355,925 -17.73 0.0249
2025-02-14 2024-12-31 13F IRON MTN INC DEL COM 46284V101 3,386,215 -254,699 355,925 0.0249
2025-05-14 2024-09-30 13F/A-2 IRON MTN INC DEL COM 46284V101 3,640,914 -14,572 -0.40 432,650 32.06 0.0314
2025-02-14 2024-09-30 13F/A-1 IRON MTN INC DEL COM 46284V101 3,640,914 -14,572 432,650 0.0314
2024-11-14 2024-09-30 13F IRON MTN INC DEL COM 46284V101 3,640,914 -14,572 432,650 0.0037
2025-05-14 2024-06-30 13F/A-2 IRON MTN INC DEL COM 46284V101 3,655,486 197,051 5.70 327,605 18.10 0.0253
2024-10-17 2024-06-30 13F/A-1 IRON MTN INC DEL COM 46284V101 3,655,486 197,051 327,605 0.0253
2024-08-14 2024-06-30 13F IRON MTN INC DEL COM 46284V101 3,655,486 197,051 327,605 0.0254
2024-10-17 2024-03-31 13F/A-2 IRON MTN INC DEL COM 46284V101 3,458,435 -227,372 -6.17 277,401 7.55 0.0223
2024-08-16 2024-03-31 13F/A-1 IRON MTN INC DEL COM 46284V101 3,458,435 -227,372 277,401 0.0026
2024-05-15 2024-03-31 13F IRON MTN INC DEL COM 46284V101 3,458,435 -227,372 277,401 0.0223
2024-08-16 2023-12-31 13F/A-1 IRON MTN INC DEL COM 46284V101 3,685,807 -536,322 -12.70 257,933 2.76 0.0227
2024-02-13 2023-12-31 13F IRON MTN INC DEL COM 46284V101 3,685,807 -536,322 257,933 0.0227
2023-11-15 2023-09-30 13F IRON MTN INC DEL COM 46284V101 4,222,129 -152,975 -3.50 251,006 0.97 0.0255
2023-08-14 2023-06-30 13F IRON MTN INC DEL COM 46284V101 4,375,104 -488,293 -10.04 248,593 -3.39 0.0245
2023-05-15 2023-03-31 13F IRON MTN INC DEL COM 46284V101 4,863,397 -200,230 -3.95 257,322 1.94 0.0276
2023-02-14 2022-12-31 13F IRON MTN INC DEL COM 46284V101 5,063,627 -307,090 -5.72 252,422 6.89 0.0287
2022-11-14 2022-09-30 13F IRON MTN INC DEL COM 46284V101 5,370,717 695,338 14.87 236,151 3.74 0.0322
2022-10-27 2022-06-30 13F/A-1 IRON MTN INC COM 46284V101 4,675,379 625,431 15.44 227,644 1.44 0.0295
2022-08-15 2022-06-30 13F IRON MTN INC COM 46284V101 4,675,379 625,431 227,644 0.0295
2022-10-27 2022-03-31 13F/A-1 IRON MTN INC COM 46284V101 4,049,948 1,195,066 41.86 224,407 50.21 0.0303
2022-05-13 2022-03-31 13F IRON MTN INC COM 46284V101 4,049,948 1,195,066 224,407 0.0303
2022-02-14 2021-12-31 13F IRON MTN INC COM 46284V101 2,854,882 -1,340,279 -31.95 149,395 -18.04 0.0184
2021-11-15 2021-09-30 13F IRON MTN INC COM 46284V101 4,195,161 1,139,861 37.31 182,280 40.97 0.0246
2021-08-23 2021-06-30 13F/A-1 IRON MTN INC COM 46284V101 3,055,300 1,123,761 58.18 129,300 80.87 0.0171
2021-08-16 2021-06-30 13F IRON MTN INC COM 46284V101 3,055,300 1,123,761 129,300 0.0035
2021-05-17 2021-03-31 13F IRON MTN INC COM 46284V101 1,931,539 -224,981 -10.43 71,486 12.45 0.0105
2021-02-16 2020-12-31 13F IRON MTN INC COM 46284V101 2,156,520 780,108 56.68 63,573 72.41 0.0098
2020-11-13 2020-09-30 13F IRON MTN INC COM 46284V101 1,376,412 -2,310,982 -62.67 36,874 -61.69 0.0071
2020-08-14 2020-06-30 13F IRON MTN INC COM 46284V101 3,687,394 -1,772,882 -32.47 96,241 -25.94 0.0213
2020-05-26 2020-03-31 13F/A-1 IRON MTN INC COM 46284V101 5,460,276 322,029 6.27 129,954 -20.64 0.0353
2020-05-15 2020-03-31 13F IRON MTN INC COM 46284V101 5,460,276 322,029 129,954 9,983.1763
2020-02-14 2019-12-31 13F IRON MTN INC COM 46284V101 5,138,247 1,033,225 25.17 163,756 23.16 0.0381
2019-11-14 2019-09-30 13F IRON MTN INC COM 46284V101 4,105,022 1,397,477 51.61 132,961 56.90 0.0352
2019-08-14 2019-06-30 13F IRON MTN INC COM 46284V101 2,707,545 -1,152,220 -29.85 84,744 -38.08 0.0226
2019-05-15 2019-03-31 13F IRON MTN INC COM 46284V101 3,859,765 -508,298 -11.64 136,868 -3.32 0.0387
2019-02-14 2018-12-31 13F IRON MTN INC COM 46284V101 4,368,063 -140,549 -3.12 141,569 -9.04 0.0424
2019-04-23 2018-09-30 13F/A-2 IRON MTN INC COM 46284V101 4,508,612 1,416,410 45.81 155,638 43.77 0.0390
2018-11-20 2018-09-30 13F/A-1 IRON MTN INC COM 46284V101 4,508,612 0 155,638 0.0390
2018-11-14 2018-09-30 13F IRON MTN INC COM 46284V101 4,508,612 1,416,410 155,638
2019-04-23 2018-06-30 13F/A-1 IRON MTN INC COM 46284V101 3,092,202 -62,653 -1.99 108,257 4.42 0.0292
2018-08-14 2018-06-30 13F IRON MTN INC COM 46284V101 3,092,202 -62,653 108,257
2019-04-23 2018-03-31 13F/A-1 IRON MTN INC COM 46284V101 3,154,855 29,669 0.95 103,670 -12.08 0.0288
2018-05-14 2018-03-31 13F IRON MTN INC COM 46284V101 3,154,855 29,669 103,670
2019-04-23 2017-12-31 13F/A-1 IRON MTN INC COM 46284V101 3,125,186 -359,099 -10.31 117,913 -13.00 0.0323
2018-02-14 2017-12-31 13F IRON MTN INC COM 46284V101 3,125,186 -359,099 117,913
2017-11-14 2017-09-30 13F IRON MTN INC COM 46284V101 3,484,285 382,401 12.33 135,539 27.17 0.0406
2017-08-11 2017-06-30 13F IRON MTN INC COM 46284V101 3,101,884 263,255 9.27 106,579 5.26 0.0322
2017-05-22 2017-03-31 13F/A-1 IRON MTN INC COM 46284V101 2,838,629 -187,111 -6.18 101,253 3.03 0.0311
2017-05-12 2017-03-31 13F IRON MTN INC COM 46284V101 2,838,629 101,253
2017-02-22 2016-12-31 13F/A-1 IRON MTN INC COM 46284V101 3,025,740 1,394,928 85.54 98,276 60.57 0.0322
2017-02-13 2016-12-31 13F IRON MTN INC COM 46284V101 3,025,740 98,276
2016-11-10 2016-09-30 13F IRON MTN INC COM 46284V101 1,630,812 -437,717 -21.16 61,203 -25.71 0.0209
2016-08-12 2016-06-30 13F IRON MTN INC COM 46284V101 2,068,529 1,602,637 343.99 82,388 421.51 0.0298
2016-05-12 2016-03-31 13F IRON MTN INC COM 46284V101 465,892 -105,102 -18.41 15,798 2.43 0.0061
2016-02-09 2015-12-31 13F IRON MTN INC COM 46284V101 570,994 68,498 13.63 15,423 -1.05 0.0056
2016-02-08 2015-09-30 13F/A-1 IRON MTN INC COM 46284V101 502,496 -105,726 -17.38 15,586 -17.33 0.0058
2015-11-09 2015-09-30 13F IRON MTN INC COM 46284V101 502,496 15,586
2015-08-12 2015-06-30 13F IRON MTN INC COM 46284V101 608,222 -543,466 -47.19 18,854 -55.12 0.0065
2015-05-14 2015-03-31 13F IRON MTN INC COM 46284V101 1,151,688 -331,824 -22.37 42,014 -26.74 0.0155
2015-02-13 2014-12-31 13F IRON MTN COM 462846106 1,483,512 224,821 17.86 57,352 39.55 0.0210
2014-12-16 2014-09-30 13F/A-1 IRON MTN COM 462846106 1,258,691 62,703 5.24 41,098 24.64 0.0158
2014-11-14 2014-09-30 13F IRON MTN COM 462846106 1,258,691 41,098
2014-05-13 2014-03-31 13F IRON MTN COM 462846106 1,195,988 451,859 60.72 32,974 45.99 0.0138
2014-02-13 2013-12-31 13F IRON MTN COM 462846106 744,129 -102,719 -12.13 22,586 -1.28 0.0096
2013-11-13 2013-09-30 13F IRON MOUNTAIN INC COM ST COM 462846106 846,848 -1,102,820 -56.56 22,880 -55.90 0.0108
2013-08-08 2013-06-30 13F IRON MOUNTAIN INC COM ST COM 462846106 1,949,668 1,949,668 51,880 0.0262
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.