Elon Musk has some pretty deep pockets, but as the world's richest man, he can arguably afford a few more lawsuits than the rest of us.
Now, the tech mogul has sent his legal eagles swarming against Microsoft and OpenAI, accusing two of the world's biggest companies of making 'wrongful gains' from his support.
As just one of four companies to have crossed the lucrative $4 trillion market cap threshold, Microsoft is up there with Nvidia, Apple, and Google, with another of the 'Big Five' earning this honor.
Like Elon Musk's own deep pockets, it's a good job that Microsoft is worth so much if it has to pay out in the latest legal wrangling.
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In federal court filings made on January 16, it confirmed that Mr. Musk has launched new proceedings against OpenAI and Microsoft. This comes after he previously put OpenAI and Apple in his crosshairs amid complaints they were unfairly knocking his xAI down the charts.
Musk's lawyer claims that OpenAI made between $65.5 billion and $109.4 billion from the billionaire's contributions when he helped co-found the company with Sam Altman in 2015. It's then argued that Microsoft's 27% stake in OpenAI means it's earned between $13.3 billion and $25.1 billion.
Steven Molo alleged: "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. A pre-eminent expert quantified the value of that."
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It's also said that a large portion of OpenAI's current $500 billion valuation is from a 'defrauded' $38 million seed money that Musk donated in 2015.
A very public falling out led to Musk leaving OpenAI in 2018, and since then, he's gone on record saying that Sam Altman and others have gone against OpenAI's initial mission of vowing to 'save humanity'.
Microsoft comes into the picture due to OpenAI's October 2025 restructuring that saw the former valuing it at the key figure of $500 billion. OpenAI is due to take on an 'investor-friendly' structure to raise capital, with the non-profit OpenAI Foundation holding equity for its for-profit arm.
Musk's filing continues: "Just as an early investor in a startup company may realise 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.”
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The specific number of $134 billion was supposedly reached under advice from financial economist C Paul Wazzan, who valued Musk's supposed input.
OpenAI has clapped back, saying that the filing is an 'unserious' demand from Musk that serves as part of a continued "harassment campaign." Both OpenAI and Microsoft have challenged Musk's claims in a separate filing.
Here, Musk's rivals asked the overseeing judge to limit what can be presented to jurors, arguing that any analysis is dismissed as "made up," "unverifiable", and "unprecedented."
They conclude that Wazzan's figures could mislead the jury, although a California judge has ruled that the trial will go ahead in April 2026.