Sam Altman, the controversial CEO of OpenAI, has a stake in social media company Reddit that’s worth over $1 billion as of post-market trading on Tuesday.

Altman controls roughly 12.2 million shares of Reddit, a company he first invested in over a decade ago. Reddit shares soared about 20% in extended trading after the compny reported better-than-expected quarterly results and issued an optimistic forecast.

At Reddit’s after-hours share price of $98, Altman’s holdings are valued at about $1.2 billion.

Prior to the surging popularity of OpenAI’s ChatGPT, which was released to the public in late 2022, Altman was best known as a startup investor and as the former president of Y Combinator. Altman’s investment portfolio includes past or present stakes in Airbnb, Uber, Instacart, Stripe and Asana, but one of his top bets was Reddit. Altman was on the social media platform’s board until around January 2022, when the company said he had recently stepped down.

Reddit went public in March at $34 a share.

Altman is among the company’s largest shareholders, behind only Condé Nast parent Advance Magazine Publishers, Chinese internet giant Tencent and Fidelity. In 2021, as the tech market was booming, Altman invested a combined $60 million in Reddit over two funding rounds, according to the company’s IPO prospectus from earlier this year.

Top shareholders were forbidden from selling Reddit shares for six months during the “lockup period,” which expired in September. There’s no indication that Altman has sold any of his stock.

Altman didn’t immediately respond to a request for comment.

Earlier this month, OpenAI closed its latest funding round at a valuation of $157 billion, including the $6.6 billion the company raised from an extensive roster of investment firms and tech companies. The company expects about $5 billion in losses on $3.7 billion in revenue this year, CNBC confirmed in September.

Altman told employees last month that there are no plans for him to receive a “giant equity stake” in the company.

In March, OpenAI said Altman was rejoining the company’s board following the conclusion of an internal investigation by U.S. law firm WilmerHale into the events that led to his sudden ouster (and rapid reinstatement) late last year.

— CNBC’s Ari Levy contributed to this report

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