IRON MOUNTAIN INC - Common Stock (IRM) Institutional Ownership

13F Institutional Holders and Ownership History from Q1 2014 to Q4 2025

Type / Class
Equity / Common Stock
Symbol
IRM on NYSE
Shares outstanding
295,211,087
Price per share
$82.95
All holders as of 30 Sep 2025
Q3 2025
Total 13F shares
250,038,524
Total reported value
$25,495,564,213
% of total 13F portfolios
0.02%
Share change
+1,211,286
Value change
+$116,964,109
Number of holders
1,001
Price from insider filings
$82.95
Reported Shares, Excluding Options vs Price
Reported Value, Excluding Options
Total Investors

Significant Owners of IRON MOUNTAIN INC - Common Stock (IRM) based on Schedule 13D/G filings

Filer Ownership Change % Holdings Value Net Change Nb Shares Change % Reporting Name Report Period
COHEN & STEERS, INC. 5.4% +27% $1,634,094,326 +$330,406,807 16,029,962 +25% Cohen & Steers, Inc. 30 Sep 2025

As of 30 Sep 2025, 1,001 institutional investors reported holding 250,038,524 shares of IRON MOUNTAIN INC - Common Stock (IRM). This represents 85% of the company’s total 295,211,087 outstanding shares.

Top 25 Institutional Shareholders

The largest institutional shareholders of IRON MOUNTAIN INC - Common Stock (IRM) together control 62% of the company’s outstanding shares — a level of ownership often associated with strong institutional conviction and long‑term capital commitment.

Institution Ownership % Shares Held Share Change % Portfolio % Holdings Value
VANGUARD GROUP INC 16% 47,253,100 +0.4% 0.07% $4,816,981,013
BlackRock, Inc. 11% 31,709,064 +1.4% 0.06% $3,232,421,986
STATE STREET CORP 5.8% 17,131,787 +1.9% 0.06% $1,759,494,141
COHEN & STEERS, INC. 5.3% 15,748,682 +14% 2.9% $1,605,263,000
GEODE CAPITAL MANAGEMENT, LLC 2.8% 8,190,580 +1.3% 0.05% $831,727,030
FMR LLC 2.7% 7,858,092 +17% 0.04% $801,053,914
Invesco Ltd. 1.7% 5,066,516 +18% 0.08% $516,480,643
DIMENSIONAL FUND ADVISORS LP 1.5% 4,348,039 +1.3% 0.1% $443,221,764
NORTHERN TRUST CORP 1.4% 4,031,566 -0.89% 0.05% $410,977,838
CHARLES SCHWAB INVESTMENT MANAGEMENT INC 1.2% 3,674,245 +1.3% 0.06% $374,552,535
MORGAN STANLEY 1.2% 3,611,399 +3% 0.02% $368,146,293
Legal & General Group Plc 1.1% 3,215,455 -2.1% 0.07% $327,783,482
Contour Asset Management LLC 1.1% 3,165,830 +36% 8.1% $322,724,710
UBS AM, A DISTINCT BUSINESS UNIT OF UBS ASSET MANAGEMENT AMERICAS LLC 1.1% 3,161,589 +598% 0.07% $322,292,383
Daiwa Securities Group Inc. 1.1% 3,151,088 +6.6% 1.1% $321,221,000
DEUTSCHE BANK AG\ 0.98% 2,890,451 -16% 0.1% $294,652,575
PRINCIPAL FINANCIAL GROUP INC 0.86% 2,527,158 -2.2% 0.13% $257,619,252
CENTERSQUARE INVESTMENT MANAGEMENT LLC 0.85% 2,514,464 +24% 2.6% $256,324,461
Pictet Asset Management Holding SA 0.83% 2,464,168 -0.46% 0.24% $251,114,890
ROYAL BANK OF CANADA 0.78% 2,298,983 +13% 0.04% $234,357,000
Nuveen, LLC 0.73% 2,142,505 +4.3% 0.06% $218,406,960
Capital World Investors 0.72% 2,117,169 0% 0.03% $215,824,208
PRUDENTIAL FINANCIAL INC 0.72% 2,113,617 +8.6% 0.26% $215,462,117
JPMORGAN CHASE & CO 0.7% 2,056,448 +4.2% 0.01% $209,634,432
Russell Investments Group, Ltd. 0.58% 1,706,435 -6.4% 0.2% $173,906,132

Institutional Holders of IRON MOUNTAIN INC - Common Stock (IRM) across Reporting Periods

Period Reported Shares, Excl. Options Value, Excl. Options Value Change Price (Median) Investors
2025 Q4 2,573,386 $214,279,303 +$4,030,638 $82.95 160
2025 Q3 250,038,524 $25,495,564,213 +$116,964,109 $101.94 1,001
2025 Q2 248,525,285 $25,494,373,784 +$803,176,563 $102.57 1,032
2025 Q1 240,741,062 $20,717,944,974 +$263,089,247 $86.04 978
2024 Q4 236,781,410 $24,894,588,495 -$258,427,735 $105.11 1,042
2024 Q3 238,451,938 $28,341,625,105 -$1,460,171,486 $118.83 1,045
2024 Q2 247,610,154 $22,212,557,225 +$1,338,701,627 $89.62 961
2024 Q1 233,231,677 $18,694,313,585 +$24,765,477 $80.21 928
2023 Q4 1,420,813 $99,491,833 -$3,491,871 $69.98 17
2023 Q3 226,310,604 $13,467,548,047 +$110,159,785 $59.45 812
2023 Q2 219,661,605 $12,486,905,095 +$4,838,236 $56.82 791
2023 Q1 223,906,566 $11,842,061,365 -$140,500,639 $52.91 766
2022 Q4 226,812,325 $11,324,894,017 +$48,340,746 $49.85 762
2022 Q3 225,271,827 $9,919,100,046 +$94,948,676 $43.97 719
2022 Q2 223,439,254 $10,886,619,442 -$1,199,958 $48.69 747
2022 Q1 223,621,866 $12,393,665,531 -$332,385,874 $55.41 756
2021 Q4 224,247,423 $11,736,500,120 +$43,412,602 $52.33 724
2021 Q3 226,206,771 $9,838,876,029 -$1,124,215 $43.45 685
2021 Q2 227,694,410 $9,645,532,653 +$24,256,802 $42.32 664
2021 Q1 200,902,556 $7,442,366,154 -$115,478,229 $37.01 605
2020 Q4 204,762,355 $6,042,627,904 -$293,336,609 $29.48 578
2020 Q3 241,353,711 $6,474,425,085 -$102,166,027 $26.79 565
2020 Q2 245,568,367 $6,417,539,509 +$9,704,486 $26.10 541
2020 Q1 242,854,119 $5,789,557,966 +$67,757,045 $23.80 501
2019 Q4 240,891,579 $7,685,545,227 -$33,458,592 $31.87 549
2019 Q3 241,496,375 $7,829,729,495 -$243,056,178 $32.39 490
2019 Q2 248,995,423 $7,798,194,010 -$61,292,481 $31.30 497
2019 Q1 254,907,324 $9,045,810,974 -$47,045,652 $35.46 513
2018 Q4 254,074,652 $8,241,172,685 +$105,249,465 $32.41 461
2018 Q3 248,610,922 $8,580,883,189 +$216,141,981 $34.52 483
2018 Q2 241,880,028 $8,467,506,550 +$12,023,577 $35.01 465
2018 Q1 249,676,217 $8,204,294,442 -$257,985,255 $32.86 455
2017 Q4 252,582,530 $9,519,099,002 +$591,759,015 $37.73 456
2017 Q3 236,306,642 $9,191,863,765 +$212,334,398 $38.90 396
2017 Q2 231,289,853 $7,947,243,080 +$108,180,265 $34.36 370
2017 Q1 228,009,429 $8,120,755,740 +$977,841,691 $35.67 358
2016 Q4 217,541,222 $7,066,206,969 +$19,516,314 $32.48 357
2016 Q3 215,714,318 $8,091,964,956 +$98,158,735 $37.53 361
2016 Q2 214,120,471 $8,524,327,091 +$413,628,970 $39.83 372
2016 Q1 201,921,099 $6,845,226,567 +$50,409,660 $33.91 329
2015 Q4 203,245,723 $5,490,896,807 -$49,801,374 $27.01 323
2015 Q3 204,905,808 $6,341,105,038 +$100,786,084 $31.02 306
2015 Q2 199,520,941 $6,184,904,001 +$148,041,940 $31.00 332
2015 Q1 195,690,973 $7,137,610,332 +$5,894,631,616 $36.48 323
2014 Q4 33,972,016 $1,313,392,000 +$1,189,574,706 $38.66 26
2014 Q3 3,202,724 $104,569,000 $0 $32.65 1
2014 Q2 0 $0 -$3,339,995 $82.95 0
2014 Q1 121,496 $3,353,169 +$561,542 $32.03 2