Sam Altman was reinstated late Tuesday as OpenAI’s chief executive, the company said, successfully reversing his ouster by the company’s board last week after a campaign waged by his allies, employees and investors.

The board of directors will be overhauled, jettisoning several members who had opposed Mr. Altman. Adam D’Angelo, the chief executive of Quora, will be the only holdover.

“We have reached an agreement in principle for Sam to return to OpenAI as CEO with a new initial board of Bret Taylor (Chair), Larry Summers, and Adam D’Angelo,” OpenAI said in a post to X. “We are collaborating to figure out the details. Thank you so much for your patience through this.”

The return of Mr. Altman and Greg Brockman, the company’s president, and the remaking of the board, capped a frenetic five days that upended OpenAI, the maker of the ChatGPT chatbot and one of the world’s highest-profile artificial intelligence companies.