Sam Altman on Tuesday said his investment in nuclear energy startup Helion, which is deep in talks on a power purchasing agreement with OpenAI, has climbed to over $1.6 billion in value.
That's up from the $375 million he invested in the company in November 2021, leading its Series E round.
While testifying at the trial over OpenAI's for-profit ambitions, Altman was presented with a document he'd signed on April 24. The exhibit gave an unusually clear picture of Altman's financial standing, showing the value of his holdings in a slate of buzzy startups.
Altman confirmed on the witness stand that he had a stake in Helion worth more than $1.6 billion as of the end of 2025. He said his first investment in the nuclear startup was in 2015, and that he's participated in multiple funding rounds since. He estimated that he owns around a third of the company, and said he also owns warrants to purchase more shares.
The exhibit also showed multimillion-dollar stakes in other tech companies. It said Altman owns $632 million of Stripe, the valuable fintech startup, and a $258 million stake in the antiaging research firm Retro Biosciences. It also listed smaller stakes, including $19 million in Trialspark, a pharmaceutical company that's rebranded to the name Formation Bio, and $3 million in Cerebras, an AI chipmaker currently preparing its IPO.
