GoKawiilMicrosoft CEO Satya Nadella passes through security at the federal courthouse during proceedings in the trial over Elon Musk's lawsuit against OpenAI in Oakland, California, on May 11, 2026.
Microsoft CEO Satya Nadella took the stand to testify in the Musk v. Altman trial in federal court in Oakland, California, on Monday.
Nadella, wearing a navy suit with a blue tie, began his testimony by answering questions about his role at Microsoft and the early days of the company's strategic partnership with OpenAI.
In 2024, Elon Musk sued OpenAI, its CEO, Sam Altman, and its president, Greg Brockman, alleging that they went back on their vow to protect the artificial intelligence company's nonprofit structure and follow its charitable mission. Microsoft is named as a defendant in the lawsuit, as Musk accuses the company of aiding and abetting OpenAI's purported breach of charitable trust.
Microsoft has been one of OpenAI's major backers since 2019, years before the company rocketed into the mainstream with the launch of its ChatGPT chatbot in late 2022. Microsoft's more than $13 billion worth of investments in OpenAI, including a $1 billion investment in 2019, a $2 billion investment in 2021 and $10 billion in 2023, have come up repeatedly over the course of the trial.
Musk, who testified late last month, said Microsoft's $10 billion investment was the key tipping point that made him believe OpenAI was violating its nonprofit mission. He testified that the scale of the investment bothered him, and it prompted him to open a legal investigation into OpenAI.
"I was concerned they were really trying to steal the charity," Musk said from the stand.