As of November 6, 2026, 4 holders' latest Schedule 13D or 13G filings report owning 5% or more of Deep Fission, Inc. The largest reported stake is Muller Elizabeth's, at 20.6%. 5 filings are on record since September 23, 2025 (Schedule 13D, September 23, 2025).
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Key facts
- · Holder: Mark N.Tompkins · Percent: 5.6% · SCHEDULE 13G/A
- · Holder: Mark N. Tompkins · Percent: 5.82% · SCHEDULE 13G/A
- · Holder: Ee Holdings Limited · Percent: 5.5% · SCHEDULE 13G
- · Holder: Muller Elizabeth · Percent: 20.6% · SCHEDULE 13D
- · Holder: Muller Richard · Percent: 10.6% · SCHEDULE 13D
Deep Fission, Inc. has 5 Schedule 13D or 13G filings on record since 2025-09-23. 4 holders' latest filing reports 5% or more of common stock, 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 |
|---|---|---|---|---|
| 20.6% | 10,541,757 | SCHEDULE 13D, 2025-09-23 | 2025-09-05 | |
| 10.6% | 5,426,406 | SCHEDULE 13D, 2025-09-23 | 2025-09-05 | |
| 5.6% | 3,158,333 | SCHEDULE 13G/A, 2026-05-15 | 2026-03-31 | |
| Ee Holdings Limited | 5.5% | 2,866,667 | SCHEDULE 13G, 2025-11-03 | 2025-09-30 |
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More on Deep Fission, Inc. and the records around it.
Deep Fission, Inc. elsewhere on the record
- IPO filing Jun 2026
- Company profile and every filing Feb 2026
- Form D filing Feb 2026
- Form D filing Sep 2025
- Who owns it
Companies that share a holder
- Muller Elizabeth also filed stake reports on 1 other company: DEEP ISOLATION NUCLEAR, INC. (Aug 2025)
- Muller Richard also filed stake reports on 1 other company: DEEP ISOLATION NUCLEAR, INC. (Aug 2025)
- Mark N. Tompkins also filed stake reports on 8 other companies: Los Altos Ventures Corp. (Jun 2026), Aeluma, Inc. (May 2026), Deep Isolation Nuclear, Inc. (May 2026)
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Purpose of Transaction (Item 4)
Muller Elizabeth
The Reporting Person acquired the Common Stock in connection with the Merger. The information contained in Item 3 of this Schedule 13D is incorporated herein by reference. The Reporting Person serves as a Director and President and Chief Executive Officer of the Issuer. Accordingly, the Reporting Person may have influence over the corporate activities of the Issuer, including activities that may relate to items described in clauses (a) through (j) of Item 4 of this Schedule 13D. Subject to the Registration Rights Agreement described in Item 6 of this Schedule 13D, the Reporting Person may, from time to time, purchase or sell securities of the Issuer as appropriate for her personal circumstances. Except as described in this Schedule 13D, the Reporting Person does not have any present plans or proposals that relate to or would result in any of the actions described in clauses (a) through (j) of Item 4 of this Schedule 13D. The Reporting Person reserves the right to formulate plans and/or proposals and to take such actions with respect to her investment in the Issuer, including any or all of the actions set forth in clauses (a) through (j) of Item 4 of this Schedule 13D.Item 4 of the SCHEDULE 13D filed 2025-09-23
Muller Richard
The Reporting Person acquired the Common Stock in connection with the Merger. The information contained in Item 3 of this Schedule 13D is incorporated herein by reference. The Reporting Person serves as a Director and Chief Technology Officer of the Issuer. Accordingly, the Reporting Person may have influence over the corporate activities of the Issuer, including activities that may relate to items described in clauses (a) through (j) of Item 4 of this Schedule 13D. Subject to the Registration Rights Agreement described in Item 6 of this Schedule 13D, the Reporting Person may, from time to time, purchase or sell securities of the Issuer as appropriate for his personal circumstances. Except as described in this Schedule 13D, the Reporting Person does not have any present plans or proposals that relate to or would result in any of the actions described in clauses (a) through (j) of Item 4 of this Schedule 13D. The Reporting Person reserves the right to formulate plans and/or proposals and to take such actions with respect to his investment in the Issuer, including any or all of the actions set forth in clauses (a) through (j) of Item 4 of this Schedule 13D.Item 4 of the SCHEDULE 13D filed 2025-09-23
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-09-23 | Muller Elizabeth | 20.6% | SCHEDULE 13D |
| 2025-09-23 | Muller Richard | 10.6% | SCHEDULE 13D |
| 2025-11-03 | Ee Holdings Limited | 5.5% | SCHEDULE 13G |
| 2025-11-14 | Mark N. Tompkins | 5.82% | SCHEDULE 13G/A |
| 2026-05-15 | Mark N.Tompkins | 5.6% | SCHEDULE 13G/A |
Questions about who owns Deep Fission, Inc.
Who owns Deep Fission, Inc.?
On this page, 4 holders' latest ownership filings report 5% or more of Deep Fission, Inc.: Muller Elizabeth (20.6%, Schedule 13D, filed 2025-09-23), Muller Richard (10.6%, Schedule 13D, filed 2025-09-23), Mark N.Tompkins (5.6%, Schedule 13G/A, filed 2026-05-15) and Ee Holdings Limited (5.5%, Schedule 13G, filed 2025-11-03).
Who are the largest shareholders of Deep Fission, Inc.?
By the share each holder's latest filing reports, the largest holders of Deep Fission, Inc. on this page are Muller Elizabeth (20.6%), Muller Richard (10.6%) and Mark N.Tompkins (5.6%).
When did Muller Elizabeth buy into Deep Fission, Inc.?
The filings give report dates, not purchase dates. The earliest filing from Muller Elizabeth on this page is the Schedule 13D, filed 2025-09-23, reporting 20.6%.
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%); 5 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.
Also on the record for Deep Fission, Inc.
| Date | Record | Figure | Our page | Source |
|---|---|---|---|---|
| June 18, 2026 | IPO filing, Form 424B4 | $16 a share | IPO filings | Source |
| June 10, 2026 | IPO filing, Form S-1/A | $16 to $18 a share | IPO filings | Source |
| May 20, 2026 | IPO filing, Form S-1 | $24 to $26 a share | IPO filings | Source |
| April 21, 2026 | IPO filing, Form S-1/A | — | IPO filings | Source |
| February 18, 2026 | Form D, private offering | $80M sold | Form D page | Source |
| February 17, 2026 | IPO filing, Form S-1 | — | IPO filings | Source |
| January 27, 2026 | IPO filing, Form S-1/A | — | IPO filings | Source |
| December 30, 2025 | IPO filing, Form S-1/A | — | IPO filings | Source |
| December 1, 2025 | IPO filing, Form S-1/A | — | IPO filings | Source |
| September 24, 2025 | Form D, private offering | — | Form D page | Source |
| September 24, 2025 | IPO filing, Form S-1/A | — | IPO filings | Source |
| September 23, 2025 | Form D, private offering | $30M sold | Form D page | Source |
The newest 12 of 13 records.
Deep Fission, Inc.: every filing and event
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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.