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.

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.