OpenAI’s Chief Scientist and Co-Founder Is Leaving the Company

Ilya Sutskever, the OpenAI co-founder and chief scientist who in November joined three other board members to force out Sam Altman, the company’s high-profile chief executive, before saying he regretted the move, is leaving the San Francisco A.I. company.

Dr. Sutskever’s departure, which the company announced in a blog post on Tuesday, closes another chapter in a story that stunned Silicon Valley and that raised questions about whether Mr. Altman and his company were prepared to lead the tech industry into the age of artificial intelligence.

After returning to OpenAI just five days after he was ousted, Mr. Altman reasserted his control and continued its push toward increasingly powerful technologies that worried some of his critics. Dr. Sutskever remained an OpenAI employee, but he never returned to work.

“This is an emotional day for all of us,” Mr. Altman said in an interview. “OpenAI would not exist without him and certainly was shaped by him.”

In a statement, Dr. Sutskever said: “I have made the decision to leave OpenAI. The company’s trajectory has been nothing short of miraculous, and I’m confident that OpenAI will build A.G.I. that is both safe and beneficial.” A.G.I., or artificial general intelligence, is an as-yet-unbuilt technology that can do anything the brain can do.

Dr. Sutskever, 38, added that he was starting a new project, but did not elaborate.

A key OpenAI researcher, Jakub Pachocki, will replace Dr. Sutskever as chief scientist at the company, which is valued at more than $80 billion, according to a recent fund-raising deal.