As of November 6, 2026, Deep Fission, Inc. is a publicly traded company (Nasdaq: FISN). The largest holder reporting an active stake on Schedule 13D is Elizabeth A. Muller, the executive officer and a director, at 20.6%. No bankruptcy or receivership appears in its SEC Form 8-K filings (Schedule 13D, September 23, 2025).
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Is Deep Fission, Inc. a real, registered company?
- Deep Fission, Inc. files with the SEC under CIK 1918102 (its SEC filings).
- Its shares are listed under the ticker FISN on Nasdaq (SEC company record).
- Incorporated in Delaware; business address in Berkeley, California, as its SEC filings state.
- Court and bankruptcy records: see Before you sign or pay below.
Before you sign or pay
- Court and bankruptcy: No federal court case or bankruptcy filing found under DEEP FISSION, INC. in our court records and SEC 8-K records (as of 2026-11-06).
- Ownership: 5%+ holders are reported on Schedule 13D or 13G; the latest names Mark N.Tompkins (filed 2026-05-15).
Who are Deep Fission, Inc.'s owners and officers?
Deep Fission, Inc.: incorporated in Delaware; business address in Berkeley, California; industry Electric Services (424B4, 2026-06-18).
Officers and directors, each with the role and the filing that names them:
- : Executive Officer, Director (Form D, 2026-02-18)
- : Executive Officer (Form D, 2026-02-18)
- : Executive Officer (Form D, 2026-02-18)
- : Director (Form D, 2026-02-18)
- : Executive Officer (Form D, 2026-02-18)
- : Director (Form D, 2026-02-18)
- : Director (Form D, 2026-02-18)
- : Director (Form D, 2026-02-18)
- : Executive Officer (Form D, 2026-02-18)
| Report | Holder | Share |
|---|---|---|
| Schedule 13G/A, 2026-05-15 | Mark N.Tompkins | 5.6% |
| Schedule 13G/A, 2025-11-14 | Mark N. Tompkins | 5.82% |
| Schedule 13G, 2025-11-03 | Ee Holdings Limited | 5.5% |
| Schedule 13D, 2025-09-23 | Muller Richard | 10.6% |
| Schedule 13D, 2025-09-23 | Muller Elizabeth | 20.6% |
Questions about who owns Deep Fission, Inc.
Who owns Deep Fission, Inc.?
On this page, 5 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 (5.82%, Schedule 13G/A, filed 2025-11-14), 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 (5.82%).
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.
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What They Do, And How The Money Works
Who Runs It, And How To Reach Them
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Which insiders own Deep Fission, Inc. shares?
Directors, officers and holders of 10% or more report their shares on Forms 3, 4 and 5. Each line is the latest such report, largest holding first.
- , the chief executive and president: 10,254,281 shares (17.4% of shares outstanding), 5,196,426 held directly and 5,057,855 indirectly (Form 4, 2025-09-09).
- , the chief technology officer and a director: 5,196,426 shares (8.8% of shares outstanding) (Form 4, 2025-09-09).
- Mark N. Tompkins: 1,891,667 shares (3.2% of shares outstanding) (Form 4, 2025-09-08).
- , a director: 324,517 shares (0.55% of shares outstanding) (Form 3, 2025-11-17).
- , the chief executive and president: 275,000 shares (0.47% of shares outstanding) (Form 4, 2025-08-28).
Shares outstanding: 58,909,588 as of 2026-10-30, from the company's latest SEC cover page.
How much has Deep Fission, Inc. raised?
| Filed | Sold | Offered |
|---|---|---|
| Form D, 2026-02-18 | $80M | $80M |
| Form D, 2025-09-24 | $0 | $120M |
| Form D, 2025-09-23 | $30M | $31.76M |
Latest IPO step: Deep Fission, Inc. filed its final IPO prospectus, ticker FISN (424B4, 2026-06-18).
IPO filings: 424B4, 2026-06-18, S-1/A, 2026-06-10, S-1, 2026-05-20, S-1/A, 2026-04-21, S-1, 2026-02-17; ticker FISN on Nasdaq Global Market.
Keep reading
More on Deep Fission, Inc. and the records around it.
Deep Fission, Inc. elsewhere on the record
- IPO filing Jun 2026
- 5%+ stake filings May 2026
- Company profile and every filing Feb 2026
- Form D filing Feb 2026
- Form D filing Sep 2025
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)
Related pages
Funding and filing history5%+ holdersIPO filings
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