Before founding OpenAI, its chief, Sam Altman, presided over Y Combinator (2014–2019), mentoring and backing numerous startups. His own startup journey also began at YC, and he has since invested in many others.
Recently, a report titled ‘The OpenAI Files’ was released on Thursday. A collaboration between the Midas Project and the Tech Oversight Project, it claims to be the “most comprehensive collection to date” of concerns regarding OpenAI.
According to the report, Altman has invested across several sectors, including artificial intelligence (AI), energy, healthcare/biotech, finance, technology, cybersecurity, and social media. His investments span AI hardware, cloud computing, energy infrastructure, nuclear fusion, longevity research, payment processing, AI-powered cybersecurity, and partnerships within social media and emerging AI startups.
It also lists companies with overlapping business ties to OpenAI, including partnerships, vendor relationships, and potential acquisitions.
In 2021, Altman invested $180 million in Retro Biosciences, a company focused on extending human lifespan and addressing age-related diseases. Retro has partnered with OpenAI, indicating potential collaboration in utilising AI for scientific advancements.
Altman also committed $375 million to Helion Energy, a nuclear fusion company working to develop sustainable energy. OpenAI has reportedly been in talks with Helion to purchase fusion energy, which could be used for its data centres, highlighting the growing need for reliable energy sources in AI development.
Altman owns approximately 7.5% of Reddit, and his stake was notably impacted when Reddit partnered with OpenAI to sell training data. This partnership resulted in a 13% increase in Reddit’s valuation, boosting Altman’s net worth by an estimated $50 million.
In 2009, Altman made an early investment in Stripe, a payment processing company, acquiring a 2% stake. Stripe is now valued at nearly $100 billion. In 2023, Stripe and OpenAI announced a partnership to integrate OpenAI’s models into Stripe’s products, linking Altman’s investment to OpenAI’s business applications.
Altman has also invested in Rewind AI, an AI hardware company that exclusively uses OpenAI’s models. Rewind AI was valued at $350 million in its most recent funding round.
In Rain AI, Altman has taken an interest in a company that manufactures chips for AI hardware. OpenAI signed a letter of intent to purchase $51 million worth of chips from Rain and is reportedly considering acquiring the company.
Altman’s investment in Exowatt ($35M in Series A, 2025) focuses on energy infrastructure, particularly for AI data centers. Exowatt’s work on providing energy solutions is critical as AI scales and demands more computational resources. He has also invested $115 million in Rescale (Series D, 2025), an AI-powered cloud computing platform that can support OpenAI’s growing cloud and computational needs.
Altman’s more recent investment in Campus ($46M in Series B, 2025) is in a company that appears to be linked to cloud or AI infrastructure, although the specific connection to OpenAI is not fully detailed.
Beyond his Investments, There is the OpenAI Startup Fund
Before founding OpenAI, its chief, Sam Altman, presided over Y Combinator (2014–2019), mentoring and backing numerous startups. His own entrepreneurial journey began there, and he has since invested in many others.
While Altman appeared on the company’s debut podcast, a report titled ‘The OpenAI Files’ was released on Thursday. A collaboration between the Midas Project and the Tech Oversight Project, it claims to be the “most comprehensive collection to date” of concerns regarding OpenAI.
According to the report, Altman has invested across several sectors, including artificial intelligence (AI), energy, healthcare/biotech, finance, technology, cybersecurity, and social media. His investments span AI hardware, cloud computing, energy infrastructure, nuclear fusion, longevity research, payment processing, AI-powered cybersecurity, and partnerships within social media and emerging AI startups.
It also lists companies with overlapping business ties to OpenAI, including partnerships, vendor relationships, and potential acquisitions.
In 2021, Altman invested $180 million in Retro Biosciences, a company focused on extending human lifespan and addressing age-related diseases. Retro has partnered with OpenAI, indicating potential collaboration in utilising AI for scientific advancements.
Altman also committed $375 million to Helion Energy, a nuclear fusion company working to develop sustainable energy. OpenAI has reportedly been in talks with Helion to purchase fusion energy, which could be used for its data centres, highlighting the growing need for reliable energy sources in AI development.
Altman owns approximately 7.5% of Reddit, and his stake was notably impacted when Reddit partnered with OpenAI to sell training data. This partnership resulted in a 13% increase in Reddit’s valuation, boosting Altman’s net worth by an estimated $50 million.
In 2009, Altman made an early investment in Stripe, a payment processing company, acquiring a 2% stake. Stripe is now valued at nearly $100 billion. In 2023, Stripe and OpenAI announced a partnership to integrate OpenAI’s models into Stripe’s products, linking Altman’s investment to OpenAI’s business applications.
Altman has also invested in Rewind AI, an AI hardware company that exclusively uses OpenAI’s models. Rewind AI was valued at $350 million in its most recent funding round.
In Rain AI, Altman has taken an interest in a company that manufactures chips for AI hardware. OpenAI signed a letter of intent to purchase $51 million worth of chips from Rain and is reportedly considering acquiring the company.
Altman’s investment in Exowatt ($35M in Series A, 2025) focuses on energy infrastructure, particularly for AI data centers. Exowatt’s work on providing energy solutions is critical as AI scales and demands more computational resources. He has also invested $115 million in Rescale (Series D, 2025), an AI-powered cloud computing platform that can support OpenAI’s growing cloud and computational needs.
Altman’s more recent investment in Campus ($46M in Series B, 2025) is in a company that appears to be linked to cloud or AI infrastructure, although the specific connection to OpenAI is not fully detailed.
Beyond his Investments, There is the OpenAI Startup Fund
OpenAI’s Startup Fund, launched in 2021, raised $175 million for its main fund and an additional $114 million through special purpose vehicles (SPVs).
The company has a growing startups team led by Marc Manara.
The fund is backed by external investors, including Microsoft, and has invested in over a dozen startups.
Anysphere, also known as Cursor and creator of the AI-driven coding assistant Cursor, secured an $8 million seed round in October 2023, led by OpenAI’s fund.
The fund also backed Chai Discovery, an AI company focused on drug discovery, which raised $30 million in its seed round. Class Companion, an edtech startup helping teachers provide personalised feedback, raised $4 million in a seed round in 2023. Another significant investment was in Descript, a platform for collaborative audio and video editing, which raised $50 million in Series C shortly after ChatGPT was released in late 2022.
In robotics, Figure AI raised $675 million in Series B in February 2024, with OpenAI’s fund also participating.
Meanwhile, Harvey AI, a legal tech startup, raised $21 million in Series A. OpenAI continued to invest in the company through later rounds, including a $300 million Series D that valued Harvey at $3 billion.
Ghost Autonomy, which developed autonomous driving software and raised $55 million in a Series E round, with $5 million from OpenAI’s fund, shut down a year later.
Other companies supported by OpenAI’s fund include Heeyo, an AI chatbot for kids that raised $3.5 million; Kick, which is building AI-powered bookkeeping tools, raising $9 million; and Mem, an AI-powered note-taking app, which secured $23.5 million in Series A.
The fund also invested in Milo, an AI personal assistant for parents, and Physical Intelligence, which develops software for robots. Another investment was in Speak, a language learning app, which raised $27 million in Series B and later $78 million in Series C.
Thrive AI, an AI health coach startup, raised $10 million through a partnership with Arianna Huffington and OpenAI’s fund. Finally, Unify, a sales tech startup, raised $19 million in seed and Series A capital from the fund.
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