Elon Musk is seeking between US$79 billion and US$134 billion in damages from OpenAI and Microsoft, alleging that the generative AI company defrauded him by abandoning its nonprofit mission and forming a partnership with the software giant.

Musk’s attorney outlined the damages claim in a court filing on Friday, a day after a United States federal judge denied OpenAI and Microsoft’s final attempt to avoid a jury trial scheduled for late April in Oakland, California.

Citing calculations from financial economist and expert witness C. Paul Wazzan, the filing claims that Musk is entitled to a portion of OpenAI’s current US$500 billion valuation, after allegedly being defrauded of the US$38 million in seed funding he contributed when helping to found the company in 2015.

“Just as an early investor in a startup company may realize gains many orders of magnitude greater than the investor’s initial investment, the wrongful gains that OpenAI and Microsoft have earned – and which Mr. Musk is now entitled to disgorge – are much larger than Mr. Musk’s initial contributions,” Musk lawyer Steven Molo wrote.

Musk departed from OpenAI’s board in 2018, founded his own AI company in 2023, and in 2024 initiated a legal battle with OpenAI CEO Sam Altman over plans to run the company as a for-profit enterprise.

OpenAI and Microsoft have denied all of Musk’s claims.

“Mr Musk’s lawsuit continues to be baseless and a part of his ongoing pattern of harassment, and we look forward to demonstrating this at trial,” OpenAI said in a statement. “This latest unserious demand is aimed solely at furthering this harassment campaign.”

OpenAI has cautioned investors that Musk may make sensational claims as the legal battle moves toward trial.