Amentum Holdings Inc.
Ownership
Ownership Structure
Who owns Amentum Holdings Inc. (AMTM)? This page shows the largest institutions and funds, the ownership structure and the latest insider transactions. 62.4% of the shares are freely tradable; institutional investors hold 107.7%.
Largest Shareholders
Institutions
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| AMERICAN SECURITIES LLC | 18.42 | 45,026,743 | +0.0 | 06/30/2026 |
| Amvescap Plc. | 10.21 | 24,954,251 | +16.2 | 06/30/2026 |
| BlackRock Inc | 7.32 | 17,906,984 | +0.4 | 06/30/2026 |
| PRIMECAP Management Company | 5.02 | 12,285,504 | +1.7 | 06/30/2026 |
| Vanguard Portfolio Management, LLC | 3.25 | 7,948,385 | +1.2 | 06/30/2026 |
| Vanguard Capital Management, LLC | 2.75 | 6,711,987 | +0.9 | 06/30/2026 |
| FMR Inc | 2.32 | 5,679,175 | +1.8 | 06/30/2026 |
| Dimensional Fund Advisors, Inc. | 2.26 | 5,537,696 | +46.2 | 06/30/2026 |
Funds
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| iShares Core S&P Small-Cap ETF | 3.75 | 9,171,825 | +0.0 | 09/30/2026 |
| Vanguard PRIMECAP Core Inv | 2.26 | 5,516,796 | +4.7 | 06/30/2026 |
Largest reported positions according to regulatory filings; stake as a percentage of shares outstanding, change versus the previous filing. Source: fundamentals data.
Insider holdings
| Person | Role | Shares | Value | As of | Type |
|---|---|---|---|---|---|
| Thompson Christopher M.T. | Director | 5,750 | 129,375 $ | Aug 14, 2026 | indirect |
Holdings as of each person's most recent SEC Form 4 filing — excluding options and RSUs, which are not shares yet. Holdings may have changed between two filings.
Insiders
Insider Transactions
| Date | Person | Role | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| Aug 14, 2026 | Thompson Christopher M.T. | Director | Other | 4,250 | 0.00 | – |
Reportable transactions by officers and major shareholders from SEC Form 4 filings. "Other" includes things like stock grants and option exercises without a buy/sell character. View all insider transactions →
Data as of: November 2, 2026 · Source: fundamental data & SEC filings (annual and quarterly reports, 10-K/10-Q)
Note: pure fact-based analysis, not investment advice and not a solicitation to buy or sell. All figures without guarantee.