Sam Altman, best known as the CEO of OpenAI, has steadily built a large and diverse investment portfolio that spans technology, biotechnology, energy, real estate, and more. While he is most widely recognized for leading the development of ChatGPT and other AI systems, his influence reaches well beyond OpenAI. Since 2019, Altman has made numerous private investments, often aligning with emerging trends in innovation and future-forward industries.
Before heading OpenAI, Altman served as president of Y Combinator between 2014 and 2019. During his time there, he worked with hundreds of startups, many of which have gone on to become major players in the tech industry. Parallel to his leadership roles, he has remained an active angel investor. Since 2010, he has participated in over 100 deals, including early investments in companies such as Stripe, Reddit, and Instacart.
Altman’s investing activity is not limited to his individual efforts. He is also the founder of Hydrazine Capital and Apollo Projects, the latter established with his brothers, Jack and Max Altman. Another vehicle, Altman Capital, is managed by Jack Altman and includes Sam as a limited partner. These firms have backed ventures across a wide range of industries including lab-grown meat, nuclear energy, education technology, longevity research, and artificial intelligence.
Since 2019, a number of his investments have shown ties to OpenAI’s ecosystem. One example is Humane, which developed the AI Pin device. Altman invested in three funding rounds for the company, which now incorporates OpenAI’s models to deliver AI-powered assistance. Slope and Warp, two other companies in his portfolio, have also acknowledged the use of OpenAI’s technology in their offerings.
Altman’s financial relationship with the AI chipmaker Rain also reflects overlapping interests. In 2019, OpenAI signed a letter of intent to spend $51 million with Rain, where Altman had previously invested during its seed round. Another notable investment is the language learning application Speak. Altman joined its Series A funding in 2022, and since then, the company has received further support from the OpenAI Startup Fund, allowing deeper technical integration with OpenAI systems.
As OpenAI secures more funding, most recently a reported $40 billion round, it is expected to continue acquiring or collaborating with companies that can support its infrastructure goals and application development. Among Altman’s recent personal or fund-based investments, three companies stand out. AirOps, which builds tools for testing and deploying AI applications, received funding in June 2024. CrewAI, which offers platforms for AI agent management, was backed in October 2024. Exowatt, which develops renewable energy systems, received investment in April 2024.
Energy and longevity represent two of Altman’s most substantial bets outside of AI. In November 2021, he committed $375 million to Helion, a nuclear fusion startup, making it his largest personal investment to date. The company later entered into an agreement with Microsoft, an OpenAI backer, to supply electricity. In the biotechnology space, he has invested $180 million in Retro Biosciences, a company focused on cellular reprogramming to extend human life spans.
Altman’s early investments have also led to several exits. He backed Codecademy, an edtech firm, in 2011. The company was acquired for $525 million by SkillSoft in 2021. He also invested in Instacart, which went public in 2023, and Cruise, which General Motors acquired in 2016.
In the SPAC market, Altman has ties to three different entities. He is executive officer at AltC Acquisition Corp., which has proposed a merger with nuclear fission company Oklo, where he serves as chairman. He also holds a board seat at Bridgetown Holdings, which merged with MoneyHero in 2023, and Bridgetown 2 Holdings, which merged with PropertyGuru in 2022.
Beyond business and technology, Altman has spent heavily in real estate. His property portfolio in San Francisco alone is valued at over $124 million. In 2020, he bought a six-bedroom, seven-bathroom mansion in Russian Hill for $27 million. However, this purchase led to a legal dispute. Altman, through an LLC, sued the developer Troon Pacific, accusing it of poor construction, inadequate oversight, and financial mismanagement during the property’s renovation. The lawsuit, filed in 2024, alleges numerous construction defects and claims repair costs exceeding $4 million. The legal proceedings are ongoing.
Despite the lawsuit, Altman has continued acquiring property in the same area. In January 2024, he purchased three adjacent homes for approximately $12.8 million each. These properties are registered under an LLC managed by his cousin, Jennifer Serralta, who also oversees other Altman-related real estate transactions. Together, these homes and the Russian Hill mansion form a large residential compound in one of San Francisco’s most expensive neighborhoods.
Altman also owns properties outside of California. In 2021, he bought a large estate in Kailua-Kona on Hawaii’s Big Island for $43 million. The property sits near a reconstructed Hawaiian temple and features a tennis court, guesthouses, and oceanfront access. The home is registered to an entity called the Sam Altman Qualified Opportunity Fund. According to Business Insider, Altman has been seen wakesurfing in the area.
In addition, he owns a 950-acre ranch in Napa Valley, California, purchased in 2020. A New York Times article from 2023 described the house on the ranch as remodeled in a mix of modern and rural styles. The property includes space for cattle and vineyards. Altman and his husband, Oliver Mulherin, spend weekends there, according to the report.
