Marathon Fusion
PrivateLast Round
Series A
Sep 12, 2026
Total Funding Raised
$10.48M
Momentum
Top 5%
of companies Caplight tracks
Company Overview
Marathon Fusion operates in Energy & Sustainability and is based in San Francisco, California. Its latest recorded funding round was a Grant round in January 2025.
Marathon Fusion is a deep tech company that develops fuel cycle technologies, including advanced pumping and isotope separation, to improve the efficiency and economics of fusion power plants.
Sector
Energy & Sustainability
Verticals
Renewable Energy, Advanced Materials
Business Model
B2B
Customer Profile
Data as a Service, Services & Consulting
AI Layer
Non-AI
Historical Pricing
Historical view of private secondary pricing and transaction trends.
Marathon Fusion Comparables
Compare Marathon Fusion with similar companies based on industry and business-model similarity.
| Company | Similarity | Market Cap |
|---|---|---|
| Fusion Fuel Cycles Inc. | 81% | |
| Crossfield Fusion Ltd | 77% | |
| Kyoto Fusioneering | 76% |
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Marathon Fusion Funding Rounds
Historical fundraising activity
| Round | Date | Amount Raised | Valuation | Investors | Sources |
|---|---|---|---|---|---|
| Series A | Sep 12, 2026 | ||||
| Grant | Jan 15, 2025 | ||||
| Grant | Aug 20, 2024 | ||||
| Seed | Jul 18, 2024 | ||||
| Accelerator | Sep 1, 2023 | ||||
Grant | Aug 3, 2023 |
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Key People
Founding team and executive leadership
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Marathon Fusion Investors
Notable investors and investment history
| Investor | Rounds |
|---|---|
| Übermorgen Ventures | Seed |
| 1517 Fund | Seed |
| Breakthrough Energy Foundation | Accelerator |
| Collaborative Fund | Seed |
| Strong Atomics | Seed |
| US Department of Energy (ARPA-E) | Grant |
Market signals
Structured signals derived from secondary market and firmographic data.
- Sep 12, 2026
Completed a Series A funding round.
- Aug 21, 2026
Monthly visitors grew 93% MoM, reaching 6.8K.
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Recent news
Latest coverage and updates
- receives_awardOct 23, 2026
Marathon Fusion, Inc. receives the ARPA-E prize for its high-risk energy research.
- expands_facilitiesOct 23, 2026
On Oct 21st '26, Marathon Fusion, Inc. says it is building a fusion reactor in California, which remains under construction.
- has_revenueOct 22, 2026
Marathon Fusion, Inc. models $223M in annual revenue from electricity alone at a gigawatt-scale fusion plant.
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Marathon Fusion Filings
Explore SEC and related filing metadata, where available.
| Type | Date | Amount Offered | Amount Sold | Filing | Pages | Download |
|---|
Filing documents are not displayed on this public page. Request access to learn about available coverage.
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Frequently Asked Questions
Common questions about Marathon Fusion's valuation, stock price, and market status.
Is Marathon Fusion a public or private company?
Marathon Fusion is a private company.
What is the current stock price of Marathon Fusion?
Marathon Fusion is a private company, so its shares have no public market price. Caplight tracks Marathon Fusion's secondary market activity and provides MarketPrice™ estimates of its share price to Caplight users.
How much is Marathon Fusion worth (valuation)?
Valuation information for Marathon Fusion is not publicly available.
Can I buy Marathon Fusion stock?
Marathon Fusion shares may be available on secondary markets subject to transfer restrictions. Caplight facilitates secondary market transactions for accredited investors.
When was Marathon Fusion's last funding round?
Marathon Fusion's most recent funding round was Series A on September 12, 2026.
Who are the main investors in Marathon Fusion?
Key investors in Marathon Fusion include 1517 Fund.
Will Marathon Fusion IPO soon?
No public IPO plans have been announced for Marathon Fusion.
How can I track Marathon Fusion secondary market activity?
Caplight tracks bids, offers, and trades in Marathon Fusion's shares on secondary markets.