8 Startups Sam Altman Invested in Outside OpenAI in 2025

Aside from becoming a household name with the breakout success of ChatGPT in 2022, OpenAI CEO Sam Altman has long been one of Silicon Valley’s most influential startup investors. Long before generative A.I. captured global attention, Altman built a reputation as a prolific angel investor whose bets helped shape the modern tech landscape, from early stakes in Stripe, Reddit and Instacart to later, high-conviction investments in nuclear energy and longevity science.

Altman’s track record...