Sam Altman shoots up on Forbes top billionaires list with a $6.5 billion net worth

Sam Altman’s fortune has climbed to more than $6.5 billion, based on Forbes’ latest estimate, after court filings pulled new details about his private company stakes into public view.

Sam’s wealth was previously placed at a little above $4.5 billion, but the new estimate includes holdings tied to companies that have had business with OpenAI, plus an indirect interest in the ChatGPT maker through Y Combinator, though Sam did not disclose the size of that OpenAI-related stake in court.

Greg Brockman, OpenAI’s president, testified that his personal stake in the company is worth close to $30 billion, while Ilya Sutskever, an OpenAI cofounder, was tied to a $7 billion holding.

Those numbers came out while Elon Musk’s lawsuit against OpenAI and Sam continued in court, with Elon seeking $150 billion in damages and asking for Sam to be removed as both an officer and board member.

Court filings put Sam’s private stakes under pressure as regulators circle OpenAI

The court document said Sam owns more than $2 billion in companies that have done business with OpenAI. That detail landed in the middle of claims from Elon and state attorneys general that Sam had conflicts tied to his personal investments.

Elon’s case includes allegations of breach of charitable trust and unjust enrichment. Sam denied those claims and told the court he stepped aside from important talks when a company involved was one he had backed.

The investment list was shown Tuesday by Steven Molo, Elon’s lead trial lawyer. Steven presented it during hearings on the lawsuit, and the document gave the fair market value of Sam’s holdings in nine companies that had OpenAI business ties as of December 31, 2025.

The biggest name on the list was Helion Energy, where Sam had a $1.7 billion stake. Helion is a private fusion power company.

Sam told the court he knew Helion’s founders personally and first put money into the company in 2015. Helion wants to build the world’s first fusion power plant, but it has no revenue yet. Private market investors have valued it at $5.4 billion.

The filing also listed a $633 million stake in Stripe, the private financial software company, and a $258 million stake in Retro Biosciences, an anti-aging drug company.

Both had deals with OpenAI. Other companies on the list included Cerebras, a chipmaker, Lattice, the people management software company formerly known as Degree, Humane, an AI device company, Software Applications, an AI software firm, and Formation Bio, the AI drug company formerly called Trialspark.

The document also said Sam had sold his stake in Reddit (RDDT) by the end of 2025. His Reddit holding was worth more than $600 million on the day Reddit went public in 2024, based on SEC filings from that period.

Regulators are now poking around too. Ten U.S. attorneys general asked the Securities and Exchange Commission on Tuesday to review OpenAI documents before a possible IPO.

Last week, the House Committee on Oversight and Government Reform asked Sam for details on how OpenAI handles conflict-of-interest risks.

Sam defends his role in Helion, Reddit, and Cerebras deals while Musk’s lawyer attacks his trust record

The Helion deal became one of the biggest parts of the hearing. Sam testified that he asked OpenAI’s board in late 2022 to look at working with Helion. He said he backed the idea because he thought it was a good deal.

Helion later signed a 2024 agreement to provide future power for OpenAI, at a time when AI companies were burning through huge amounts of electricity for data centers and model training.

Sam stepped down from Helion’s board in March 2026 while OpenAI and Helion were discussing a larger agreement. On the 2024 deal, Sam told the court he was “recused from it on both sides” and said he did not sign the agreement.

Steven also questioned Sam about OpenAI’s May 2024 content partnership with Reddit (RDDT). Steven said Sam had an “obvious conflict” because of his ties to Reddit.

Sam said OpenAI’s board had to approve the final terms and said other people were present during the talks. “We decided that the board would approve any final terms,” Sam said. “I had other people in the room with me. This was a well-discussed standard corporate recusal.”

Steven then brought up OpenAI’s $10 billion computing deal with Cerebras. Sam has a stake in Cerebras worth about $3.2 million, according to the court document.

Steven also tried to paint Sam as someone the court should not trust. He referred to earlier concerns from OpenAI employees, including Dario Amodei, who later became CEO of Anthropic.

After introducing Dario, Steven also pointed to former OpenAI board members and a long New Yorker article that questioned whether Sam could be trusted.

If you're reading this, you’re already ahead. Stay there with our newsletter.