Marathon Fusion
Marathon Fusion is a San Francisco-based fusion technology startup founded in 2023 that develops tritium fuel processing, isotope separation, and mercury-to-gold transmutation technologies for fusion power plant developers, with signed Letters of Intent from Commonwealth Fusion Systems and Helion Energy.
- Company typePrivate
- Founded2023
- HeadquartersSan Francisco, United States
- Headcount1–10
- GTM typeB2B
- OfferingHardware or Manufacturing
What Marathon Fusion does
Marathon Fusion is a private fusion technology company founded in 2023 and headquartered at 150 Mississippi St in San Francisco. The company designs, engineers, and scales fuel cycle technologies intended to make fusion power plants economically viable. Its work spans three technical pillars: (1) advanced pumping technologies — specifically proprietary metal foil pumps — to improve tritium burn efficiency and processing speed; (2) isotope separation for critical materials used in fusion and other industrial applications; and (3) neutron-driven transmutation, including a published (non-peer-reviewed) methodology for converting mercury-198 into gold via deuterium-tritium fusion reactions, which the company estimates could yield approximately 5,000 kg of gold per gigawatt of fusion capacity annually, valued at over $550 million per GW per year.
The company's go-to-market is direct enterprise sales to fusion power plant developers. As of mid-2024, Marathon Fusion has signed Letters of Intent with Commonwealth Fusion Systems and Helion Energy — two of the most prominent private fusion developers — for deployment of its fuel processing technology. Revenue, once generated, is expected to flow from technology licensing and hardware sales to fusion operators, with a potential secondary stream from gold and medical radioisotope production enabled by the transmutation technology. The company is currently pre-revenue.
Marathon Fusion has raised approximately $6.9M in disclosed venture funding through a July 2024 seed round co-led by 1517 Fund and Anglo American, supplemented by over $4.5M in non-dilutive ARPA-E grants (CREATE Award in August 2023, INFUSE Award in 2024, and inclusion in the $147M ARPA-E OPEN announcement in January 2025). The company claims over $18M in cumulative funding since founding. Its team of more than 20 named members — including 10 PhDs in physics, chemistry, materials science, and chemical engineering — draws prior experience from SpaceX, Helion Energy, TAE Technologies, Tokamak Energy, Princeton Plasma Physics Laboratory, Tesla, Argonne National Lab, Fermilab, and Commonwealth Fusion Systems, with scientific advisors from UC Berkeley, Princeton PPPL, MIT, and ARPA-E.
Marathon Fusion firmographics
Firmographics- Name
- Marathon Fusion
- Legal name
- Marathon Fusion
- Website
- https://marathonfusion.com
- Company type
- Private
- Founded year
- 2023
- Operating status
- Operating
- Headcount range
- 1–10 employees
- Short description
- Marathon Fusion is a San Francisco-based fusion technology startup founded in 2023 that develops tritium fuel processing, isotope separation, and mercury-to-gold transmutation technologies for fusion power plant developers, with signed Letters of Intent from Commonwealth Fusion Systems and Helion Energy.
- Ownership category
- akta.pro rank
Marathon Fusion industry classification
Industry- Product category
- Nuclear Fusion Equipment
- NAICS
- Petrochemical Manufacturing (325110), Power Boiler and Heat Exchanger Manufacturing (332410)
- akta.pro primary industry
- Fuel Cycle Support Services (Engineering, licensing support, conversion/enrichment contracting) (EUAKACAL)
- akta.pro secondary industries
- Advanced & Non‑LWR Fuel Manufacturing (TRISO, metallic fuels, HALEU fuels) (EUAKACAG), Reactor Refueling & Fuel Handling Systems (Cranes, Machines, Transfer Systems) (EUAKADAN), Nuclear Fuel Cycle for Power Generation (Uranium, Conversion, Enrichment, Fuel Fabrication) (EUACADAK)
Keywords
Where Marathon Fusion is headquartered
LocationHeadquarters
- HQ city
- San Francisco
- HQ country
- United States
- HQ region
- North America
Offices1 record
Markets served
Marathon Fusion business model
Business model- GTM type
- B2B
- Offering type
- Hardware or Manufacturing
- Cost components
- Technology or R&D, Personnel, Operations, Marketing or Sales, Infrastructure
Revenue model
- Fuel Processing Technology Licensing/Sale: Technology deployment and licensing to fusion power plant developers including Commonwealth Fusion Systems and Helion Energy through signed Letters of Intent
- Gold and Radioisotope Production: Secondary value stream from transmutation technology producing gold and medical isotopes from fusion reactors - estimated potential value of over $550M per GW annually
- Critical Isotope Supply: Supplying critical materials for fusion and other industrial applications through isotope separation technology
Go-to-market motion3 records
Distribution channels1 record
Marketing channels6 records
Marathon Fusion product offering
Product offeringCore offering
Marathon Fusion designs, engineers, and scales next-generation fuel cycle technologies for the fusion energy industry. Its core offerings span three areas: (1) fuel processing via advanced metal foil pumps that improve tritium burn efficiency and processing speed for fusion power plants; (2) transmutation (referred to internally as "alchemy") that uses neutron-driven reactions to produce radioisotopes and gold as a secondary value stream; and (3) isotope separation to supply critical materials for fusion and industrial applications.
Product overview
Marathon Fusion develops a unified portfolio of fuel cycle technologies for the fusion industry, organized around three core offerings: Transmutation (Alchemy) for neutron-driven gold production from fusion reactors, Fuel Processing for advanced pumping technologies to improve tritium burn efficiency and processing speed, and Isotope Separation for supplying critical materials for fusion and other industrial applications. These technologies are designed to improve the economics and efficiency of fusion power plants.
Differentiator
Problem solved
Functional benefit
Products and services
- Fuel Processing Technology Advanced metal foil pumps and fuel processing systems designed to improve tritium burn efficiency and processing speed for fusion power plants. Sold/licensed to fusion power plant developers building commercial reactors.
- Transmutation (Alchemy) Neutron-driven transmutation process that produces radioisotopes and approximately 5,000 kg of gold per gigawatt of fusion energy annually, providing fusion plant operators with a secondary revenue stream beyond electricity.
- Isotope Separation Technology for separating and supplying critical isotopes required for fusion reactors and other industrial applications.
Quantifiable outcome
- 5,000 kg gold per GW per year from transmutation
- +3 more outcomes
Companies that use Marathon Fusion
Customer profileNamed customers2 records
Segments2 records
Ideal customer profiles1 record
Marathon Fusion technology and API
TechnologyTechnology focussed Yes
API detail
- Has API
- No
- API docs
- API detail
Core technology
AI maturity
App detail
Feature3 records
Marathon Fusion partnerships and signals
Strategic signalPartnerships
Two partnerships are on record, tiered core.
- Commonwealth Fusion SystemscoreSigned Letter of Intent for fuel processing technology deployment. Commonwealth Fusion Systems is a leading fusion startup developing compact high-field superconducting tokamak technology.
- Helion EnergycoreSigned Letter of Intent for fuel processing technology deployment. Helion Energy is developing a sixth-generation fusion technology targeting direct electricity generation.
Scale indicators5 records
Recent moves6 records
Expansion highlights5 records
Marathon Fusion competitors and assessment
Company assessmentDirect peers
- Kyoto Fusioneering: Japan- and UK-based fusion plant engineering company developing tritium fuel cycle systems, blanket technology, and gyrotrons for fusion power plants. Closest direct peer to Marathon Fusion given its focus on enabling fusion plant subsystems rather than the reactor itself.
- SHINE Technologies: US-based fusion-adjacent company producing medical and industrial isotopes using fusion-relevant neutron source technology. Comparable because it pursues a non-power revenue stream (isotopes) enabled by fusion technology, mirroring Marathon's transmutation/isotope separation thesis.
Emerging players
- Curio: US startup developing nuclear waste transmutation technology using advanced reactor designs. Comparable as a niche player pursuing neutron-driven transmutation for valuable outputs, though focused on waste streams rather than fusion power plant integration.
- Zap Energy: US shear-flow Z-pinch fusion startup featured alongside Marathon in The New York Times coverage. Comparable as a fusion ecosystem participant at similar stage pursuing a different confinement approach; potential long-term customer for fuel cycle technology.
- Type One Energy: US stellarator fusion startup. Operates in the same broader fusion technology ecosystem; potential future customer for fuel processing and isotope separation as it advances toward pilot plant deployment.
- Stellaria: France-based fusion startup developing laser-driven inertial confinement approaches with focus on tritium and fuel cycle challenges. Comparable as a fusion fuel-cycle-focused startup in the European ecosystem pursuing adjacent fuel handling problems.
Broad incumbents
- Commonwealth Fusion Systems: Leading private fusion developer (SPARC tokamak). Operates in the same fusion ecosystem and is a Marathon customer via LOI, but competes for talent and capital in the broader fusion narrative; could also internalize fuel cycle capabilities.
- Helion Energy: Fusion developer pursuing pulsed FRC-based direct electricity generation. Marathon customer via LOI and a fellow fusion ecosystem participant, with potential to internalize fuel cycle work over time.
- TAE Technologies: Long-running fusion developer pursuing field-reversed configuration plasmas with a boron-fueled p-B reaction. Operates in the same fusion ecosystem; potential future customer for fuel processing and isotope separation technology.
- Tokamak Energy: UK-based spherical tokamak developer pursuing compact fusion. Adjacent player in the same fusion landscape, with deep expertise in tritium and fuel handling that could make it a future partner or competitor.
Market position
Strengths5 records
Weaknesses5 records
Competitive moat3 records
Key risks6 records
Key highlights6 records
Customer concentration
Marathon Fusion social profiles
Digital presenceMarathon Fusion financial estimates
Financial estimateRevenue estimate
Valuation estimate
Marathon Fusion leadership team
Management profileNumber of profiles
Profiles2 records
Marathon Fusion funding detail
Funding detailFunding overview
Funding rounds5 records
Investors9 records
Funding detail is available on the Subscription and Enterprise plan.Contact sales →
Marathon Fusion M&A and investment
M&A and investmentM&A
Investments
M&A and investment is available on the Subscription and Enterprise plan.Contact sales →
Frequently asked questions about Marathon Fusion
What does Marathon Fusion do?
Marathon Fusion designs, engineers, and scales next-generation fuel cycle technologies for the fusion energy industry. Its core offerings span three areas: (1) fuel processing via advanced metal foil pumps that improve tritium burn efficiency and processing speed for fusion power plants; (2) transmutation (referred to internally as "alchemy") that uses neutron-driven reactions to produce radioisotopes and gold as a secondary value stream; and (3) isotope separation to supply critical materials for fusion and industrial applications.
Is Marathon Fusion a public or private company?
Marathon Fusion is a private company. It is classified as venture growth investor backed and is currently operating.
When was Marathon Fusion founded?
Marathon Fusion was founded in 2023. It employs 1 to 10 people.
Where is Marathon Fusion based?
Marathon Fusion is headquartered in San Francisco, United States, in the North America region.
How does Marathon Fusion make money?
Three revenue lines are on record. Fuel Processing Technology Licensing/Sale is the primary driver. The others are gold and Radioisotope Production and critical Isotope Supply.
Who are Marathon Fusion's main competitors?
Direct peers on record are Kyoto Fusioneering and SHINE Technologies. Emerging players are Curio, Zap Energy, Type One Energy and Stellaria. Broad incumbents are Commonwealth Fusion Systems, Helion Energy, TAE Technologies and Tokamak Energy.
Does Marathon Fusion have an API?
No public API is recorded for Marathon Fusion.
What industry is Marathon Fusion in?
Marathon Fusion's product category is Nuclear Fusion Equipment. Its primary akta.pro industry code is EUAKACAL, Fuel Cycle Support Services (Engineering, licensing support, conversion/enrichment contracting), with a secondary code of EUAKACAG, Advanced & Non‑LWR Fuel Manufacturing (TRISO, metallic fuels, HALEU fuels). Its NAICS code is 325110.