Amentum Holdings Inc. (AMTM) Ownership
AMTM ownership summary
as of October 18, 2026- Institutions
- 109.3% of shares outstanding
- Insiders
- 1.17% of shares outstanding
- Shares outstanding
- 244.5M
- Float
- 152.5M shares available to trade
- Short interest
- 8.01% 12.3M shares short
- Days to cover
- 7.13 short interest up 1.9% vs prior month
- Institutions 109.26%
- Insiders 1.17%
AMTM top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | AMERICAN SECURITIES LLC | 18.42% | 45.0M | $878.9M | — | June 30, 2026 |
| 2 | Amvescap Plc. | 10.21% | 25.0M | $487.1M | +3.5M (+16.2%) | June 30, 2026 |
| 3 | BlackRock Inc | 7.32% | 17.9M | $349.5M | +65,701 (+0.4%) | June 30, 2026 |
| 4 | PRIMECAP Management Company | 5.02% | 12.3M | $239.8M | +200,210 (+1.7%) | June 30, 2026 |
| 5 | Legacy Advisors, LLC | 3.71% | 9.1M | $177.0M | +1,399 (+0.0%) | June 30, 2026 |
| 6 | Vanguard Portfolio Management, LLC | 3.25% | 7.9M | $155.2M | +95,434 (+1.2%) | June 30, 2026 |
| 7 | Vanguard Capital Management, LLC | 2.75% | 6.7M | $131.0M | +61,108 (+0.9%) | June 30, 2026 |
| 8 | FMR Inc | 2.32% | 5.7M | $110.9M | +100,789 (+1.8%) | June 30, 2026 |
| 9 | Dimensional Fund Advisors, Inc. | 2.26% | 5.5M | $108.1M | +1.8M (+46.2%) | June 30, 2026 |
| 10 | State Street Corp | 2.11% | 5.2M | $100.6M | +72,731 (+1.4%) | June 30, 2026 |
| 11 | Frontier Capital Management CO Inc | 1.69% | 4.1M | $80.9M | −786,239 (−15.9%) | June 30, 2026 |
| 12 | Geode Capital Management, LLC | 1.11% | 2.7M | $53.0M | −97,855 (−3.5%) | June 30, 2026 |
| 13 | The Goldman Sachs Group Inc | 1.11% | 2.7M | $52.9M | +1.6M (+139.7%) | June 30, 2026 |
| 14 | Morgan Stanley - Brokerage Accounts | 1.09% | 2.7M | $52.0M | +427,416 (+19.1%) | June 30, 2026 |
| 15 | MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. | 0.95% | 2.3M | $45.3M | −466,553 (−16.8%) | June 30, 2026 |
| 16 | Thompson, Siegel & Walmsley LLC | 0.93% | 2.3M | $44.5M | +756,061 (+49.5%) | June 30, 2026 |
| 17 | Millennium Management LLC | 0.87% | 2.1M | $41.5M | +1.5M (+237.2%) | June 30, 2026 |
| 18 | Charles Schwab Investment Management Inc | 0.87% | 2.1M | $41.4M | +52,172 (+2.5%) | June 30, 2026 |
| 19 | Thrivent Financial For Lutherans | 0.86% | 2.1M | $41.1M | +5,345 (+0.3%) | June 30, 2026 |
| 20 | Bank of America Corp | 0.84% | 2.0M | $39.9M | −362,144 (−15.1%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 15 holders added 10.1M shares and 4 cut 1.7M.
AMTM top mutual fund and ETF holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | iShares Core S&P Small-Cap ETF | 3.75% | 9.2M | $179.0M | +2,130 (+0.0%) | September 30, 2026 |
| 2 | Vanguard PRIMECAP Core Inv | 2.26% | 5.5M | $107.7M | +246,677 (+4.7%) | June 30, 2026 |
| 3 | Vanguard MStar Total Stk Mkt Idx Invest | 1.91% | 4.7M | $91.1M | −6,662 (−0.1%) | August 31, 2026 |
| 4 | Invesco Small Cap Value A | 1.84% | 4.5M | $87.7M | +266,288 (+6.3%) | August 31, 2026 |
| 5 | Vanguard Small Cap Index | 1.38% | 3.4M | $65.8M | +819 (+0.0%) | August 31, 2026 |
| 6 | Invesco Value Opportunities A | 1.27% | 3.1M | $60.6M | +161,603 (+5.5%) | August 31, 2026 |
| 7 | Fidelity Value | 1.15% | 2.8M | $55.1M | +159,500 (+6.0%) | August 31, 2026 |
| 8 | Vanguard Capital Opportunity Inv | 1.03% | 2.5M | $48.9M | −77,686 (−3.0%) | June 30, 2026 |
| 9 | Vanguard MStar Small Cap Value Index | 0.88% | 2.1M | $41.8M | +1,696 (+0.1%) | August 31, 2026 |
| 10 | PRIMECAP Odyssey Stock | 0.77% | 1.9M | $36.7M | +25,311 (+1.4%) | June 30, 2026 |
| 11 | VanEck Defense ETF A USD Acc | 0.77% | 1.9M | $36.6M | +1,591 (+0.1%) | September 30, 2026 |
| 12 | State Street SPDR Port S&P 600 Sm CpETF | 0.57% | 1.4M | $27.3M | — | September 30, 2026 |
| 13 | iShares S&P Small-Cap 600 Value ETF | 0.53% | 1.3M | $25.4M | — | September 30, 2026 |
| 14 | DFA US Targeted Value I | 0.48% | 1.2M | $22.9M | +55,072 (+4.9%) | August 31, 2026 |
| 15 | Dimensional US Targeted Value ETF | 0.46% | 1.1M | $22.1M | +781 (+0.1%) | September 30, 2026 |
| 16 | Dimensional US Small Cap Value ETF | 0.42% | 1.0M | $19.8M | +5,480 (+0.5%) | September 24, 2026 |
| 17 | Vanguard Tax-Managed Small Cap Adm | 0.41% | 997K | $19.5M | — | August 31, 2026 |
| 18 | Fidelity Stock Selector Small Cap | 0.39% | 942K | $18.4M | — | July 31, 2026 |
| 19 | Invesco S&P SmallCap 600 Revenue ETF | 0.38% | 927K | $18.1M | +1,345 (+0.1%) | September 30, 2026 |
| 20 | DFA US Small Cap Value I | 0.34% | 826K | $16.1M | +172,815 (+26.5%) | August 31, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
AMTM insider transactions
latest 2| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2025-02-18 | Barbara Loughran | Buy | $21.23 | 4,600 | $97,658 |
| 2025-02-12 | Steven J Demetriou | Buy | $20.81 | 100,000 | $2.1M |
Reported trades by company officers, directors and other filers (including disclosures by members of Congress where EODHD lists them). "—" where the filing gives no share count.
AMTM shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns AMTM
Institutional investors own 109.3% of Amentum's shares and insiders 1.17%. The largest holder is AMERICAN SECURITIES LLC with 18.42% of the shares (45.0M), as of June 30, 2026. Among the top 20 institutions, 15 added shares and 4 reduced their stake in the latest filings. Short interest is 8.01% of the float, or 7.13 days of average trading volume.
Related: AMTM analyst forecast, AMTM key metrics. See the AMTM stock overview for the latest quote and news.
AMTM ownership FAQ
Who owns the most Amentum stock?
The largest shareholders of Amentum are AMERICAN SECURITIES LLC (18.42%), Amvescap Plc. (10.21%), BlackRock Inc (7.32%), PRIMECAP Management Company (5.02%), Legacy Advisors, LLC (3.71%).
What percentage of Amentum is owned by institutions?
Institutions hold 109.3% of Amentum's shares outstanding; insiders hold 1.17%.
Which funds own Amentum?
The largest fund holders of Amentum are iShares Core S&P Small-Cap ETF (3.75%), Vanguard PRIMECAP Core Inv (2.26%), Vanguard MStar Total Stk Mkt Idx Invest (1.91%), Invesco Small Cap Value A (1.84%), Vanguard Small Cap Index (1.38%).
What is Amentum's short interest?
12.3M shares of Amentum were sold short, 8.01% of the float; at the average daily volume it would take 7.13 days to cover.
Are insiders buying or selling Amentum?
Of the latest 2 reported insider transactions in Amentum (since February 12, 2025), 2 were purchases and 0 were sales.
How many shares of Amentum are outstanding?
Amentum has 244.5M shares outstanding, of which 152.5M are in the public float.