As of November 10, 2026, 4 holders' latest Schedule 13D or 13G filings report owning 5% or more of GP-Act III Acquisition Corp. The largest reported stake is Polar Asset Management Partners Inc.'s, at 11.1%. 12 filings are on record since August 12, 2025 (Schedule 13G, June 4, 2026).
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Key facts
- · Reporting person: W. R. Berkley Corporation · Sole voting: 0 · Shared voting: 1,016,312 · Sole dispositive: 0 · Shared dispositive: 1,016,312 · SCHEDULE 13G, 2026-11-09
- · Reporting person: AQR Capital Management, LLC · Sole voting: 0 · Shared voting: 1,400,000 · Sole dispositive: 0 · Shared dispositive: 1,400,000 · SCHEDULE 13G/A, 2026-08-14
- · Reporting person: First Trust Merger Arbitrage Fund · Sole voting: 0 · Shared voting: 0 · Sole dispositive: 0 · Shared dispositive: 0 · SCHEDULE 13G/A, 2026-08-14
- · Reporting person: Karpus Management, Inc. · Sole voting: 0 · Shared voting: 0 · Sole dispositive: 0 · Shared dispositive: 0 · SCHEDULE 13G/A, 2026-06-05
- · Reporting person: Polar Asset Management Partners Inc. · Sole voting: 1,800,000 · Shared voting: 0 · Sole dispositive: 1,800,000 · Shared dispositive: 0 · SCHEDULE 13G, 2026-06-04
GP-Act III Acquisition Corp. has 12 Schedule 13D or 13G filings on record since 2025-08-12. 4 holders' latest filing reports 5% or more of class a ordinary shares, par value $0.0001 per share. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| Polar Asset Management Partners Inc. | 11.1% | 1,800,000 | SCHEDULE 13G, 2026-06-04 | 2026-05-31 |
| AQR Capital Management, LLC | 8.66% | 1,400,000 | SCHEDULE 13G/A, 2026-08-14 | 2026-06-30 |
| Meteora Capital, LLC | 6.7% | 1,926,999 | SCHEDULE 13G, 2025-08-14 | 2025-06-30 |
| W. R. Berkley Corporation | 6.3% | 1,016,312 | SCHEDULE 13G, 2026-11-09 | 2026-09-30 |
| Picton Mahoney Asset Management | 4.78% | 1,375,000 | SCHEDULE 13G/A, 2026-04-27 | 2026-03-31 |
| MMCAP International Inc. SPC | 4.44% | 1,275,000 | SCHEDULE 13G/A, 2025-08-12 | 2025-06-30 |
| Karpus Management, Inc. | 0% | 0 | SCHEDULE 13G/A, 2026-06-05 | 2026-05-29 |
| Bank of Montreal | 0% | 0 | SCHEDULE 13G/A, 2026-02-12 | 2025-12-31 |
| First Trust Merger Arbitrage Fund | 0% | 0 | SCHEDULE 13G/A, 2026-08-14 | 2026-06-30 |
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Keep reading
More on GP-Act III Acquisition Corp. and the records around it.
Companies that share a holder
- Picton Mahoney Asset Management also filed stake reports on 20 other companies: Blue Water Acquisition Corp. III (Oct 2026), Launch One Acquisition Corp. (Oct 2026), Pono Capital Four, Inc. (Oct 2026)
- First Trust Merger Arbitrage Fund also filed stake reports on 47 other companies: TCW SPECIALTY LENDING LLC (Sep 2026), Blue Foundry Bancorp (Aug 2026), Centurion Acquisition Corp. (Aug 2026)
- Bank of Montreal also filed stake reports on 49 other companies: Akari Therapeutics Plc (Aug 2026), Alarm.com Holdings, Inc. (Aug 2026), North American Construction Group Ltd. (Aug 2026)
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Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| Polar Asset Management Partners Inc. | 1,800,000 | 0 | 1,800,000 | 0 | SCHEDULE 13G, 2026-06-04 |
| AQR Capital Management, LLC | 0 | 1,400,000 | 0 | 1,400,000 | SCHEDULE 13G/A, 2026-08-14 |
| AQR Capital Management Holdings, LLC | 0 | 1,400,000 | 0 | 1,400,000 | SCHEDULE 13G/A, 2026-08-14 |
| AQR Arbitrage, LLC | 0 | 1,400,000 | 0 | 1,400,000 | SCHEDULE 13G/A, 2026-08-14 |
| AQR Global Alternative Investment Offshore Fund, L.P. | 0 | 838,420 | 0 | 838,420 | SCHEDULE 13G/A, 2026-08-14 |
| AQR Capital Management GP Ltd. | 0 | 838,420 | 0 | 838,420 | SCHEDULE 13G/A, 2026-08-14 |
| W. R. Berkley Corporation | 0 | 1,016,312 | 0 | 1,016,312 | SCHEDULE 13G, 2026-11-09 |
| Berkley Insurance Company | 0 | 1,016,312 | 0 | 1,016,312 | SCHEDULE 13G, 2026-11-09 |
| Karpus Management, Inc. | 0 | 0 | 0 | 0 | SCHEDULE 13G/A, 2026-06-05 |
| First Trust Merger Arbitrage Fund | 0 | 0 | 0 | 0 | SCHEDULE 13G/A, 2026-08-14 |
| First Trust Capital Management L.P. | 0 | 0 | 0 | 0 | SCHEDULE 13G/A, 2026-08-14 |
| First Trust Capital Solutions L.P. | 0 | 0 | 0 | 0 | SCHEDULE 13G/A, 2026-08-14 |
| FTCS Sub GP LLC | 0 | 0 | 0 | 0 | SCHEDULE 13G/A, 2026-08-14 |
The latest filing identifies GP-Act III Acquisition Corp. by CUSIP G4035N103 and gives its principal executive office as 300 Park Avenue, 2nd Floor, New York, NY 10022 (SCHEDULE 13G, 2026-11-09).
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-08-12 | MMCAP International Inc. SPC | 4.44% | SCHEDULE 13G/A |
| 2025-08-14 | Karpus Management, Inc. | 6.51% | SCHEDULE 13G/A |
| 2025-08-14 | Polar Asset Management Partners Inc. | 4.1% | SCHEDULE 13G/A |
| 2025-08-14 | Meteora Capital, LLC | 6.7% | SCHEDULE 13G |
| 2025-11-13 | Bank of Montreal | 5.14% | SCHEDULE 13G |
| 2026-02-12 | Bank of Montreal | 0% | SCHEDULE 13G/A |
| 2026-04-27 | Picton Mahoney Asset Management | 4.78% | SCHEDULE 13G/A |
| 2026-06-04 | Polar Asset Management Partners Inc. | 11.1% | SCHEDULE 13G |
| 2026-06-05 | Karpus Management, Inc. | 0% | SCHEDULE 13G/A |
| 2026-08-14 | AQR Capital Management, LLC | 8.66% | SCHEDULE 13G/A |
| 2026-08-14 | First Trust Merger Arbitrage Fund | 0% | SCHEDULE 13G/A |
| 2026-11-09 | W. R. Berkley Corporation | 6.3% | SCHEDULE 13G |
Questions about who owns GP-Act III Acquisition Corp.
Who owns GP-Act III Acquisition Corp.?
On this page, 4 holders' latest ownership filings report 5% or more of GP-Act III Acquisition Corp.: Polar Asset Management Partners Inc. (11.1%, Schedule 13G, filed 2026-06-04), AQR Capital Management, LLC (8.66%, Schedule 13G/A, filed 2026-08-14), Meteora Capital, LLC (6.7%, Schedule 13G, filed 2025-08-14) and W. R. Berkley Corporation (6.3%, Schedule 13G, filed 2026-11-09).
Who are the largest shareholders of GP-Act III Acquisition Corp.?
By the share each holder's latest filing reports, the largest holders of GP-Act III Acquisition Corp. on this page are Polar Asset Management Partners Inc. (11.1%), AQR Capital Management, LLC (8.66%) and Meteora Capital, LLC (6.7%).
When did Polar Asset Management Partners Inc. buy into GP-Act III Acquisition Corp.?
The filings give report dates, not purchase dates. The earliest filing from Polar Asset Management Partners Inc. on this page is the Schedule 13G/A, filed 2025-08-14, reporting 4.1%; its latest, Schedule 13G filed 2026-06-04, reports 11.1%. That earliest filing is itself an amendment, which updates an earlier report.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 12 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
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Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.