Musk sues OpenAI and Microsoft for $134 billion

The US-based billionaire has claimed both companies received “wrongful gains” from his early support

Elon Musk is asking OpenAI and Microsoft to pay him damages amounting to $134 billion, according to a court filing submitted by his lawyer on Friday. The US-based billionaire claims that the company behind ChatGPT obtained “wrongful gains” from his early financial support.

The tech entrepreneur was allegedly defrauded of the $38 million in seed money he donated to OpenAI in 2015, the filing said, stating that he is now entitled to a share of the company’s current $500 billion valuation.

OpenAI gained between $65.5 billion and $109.4 billion from that funding, the filing said. Microsoft, which has been investing in the company since 2019 and holds 27% of shares in OpenAI Group PBC, gained between $13.3 billion and $25.1 billion, according to the document.

“Without Elon Musk, there’d be no OpenAI. He provided the bulk of the seed funding, lent his reputation, and taught them all he knows about scaling a business,” the billionaire’s lead trial lawyer, Steven Molo, told Reuters, citing estimates by an expert witness, financial economist C. Paul Wazzan, who is mentioned in the document.

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The ChatGPT creator dismissed Musk’s demands as “baseless” and called them part of a “harassment” campaign. Microsoft did not comment on the issue of compensation.

The two co-defendants submitted a separate filing on Friday asking the judge to exclude Wazzan’s analysis, calling it “made up” and “unverifiable.”

Musk helped co-found OpenAI in 2015, investing approximately $45 million in total, but left the board in 2018 due to strategic disagreements with its CEO, Sam Altman. The billionaire has since emerged as a vocal critic of OpenAI’s commercialization efforts and close partnership with Microsoft.

In February 2025, he offered to buy OpenAI for $97.4 billion to counter its transition to a for-profit model. Altman dismissed the offer and mockingly suggested buying Musk’s social media platform, X, for $9.74 billion instead.

OpenAI dethroned Musk’s SpaceX as the world’s most valuable private tech firm in October when it reached a valuation of $500 billion after its current and former employees sold roughly $6.6 billion worth of shares to a consortium of investors.