Sam Altman has been reinstated as OpenAI's CEO, accompanied by a newly appointed board of directors.

Sam Altman, the ousted CEO of ChatGPT-maker OpenAI, is returning to the company he founded, accompanied by a newly constituted board of directors.

The announcement, made late Tuesday, brings to an end a tumultuous week that saw OpenAI's leadership team ousted and the company's future thrown into uncertainty. The new board will be chaired by Bret Taylor, the former co-CEO of Salesforce and a former member of Twitter's board of directors. Other members will include former U.S. Treasury Secretary Larry Summers and Quora CEO Adam D'Angelo.

The previous board of directors, which included D'Angelo, had declined to provide specific reasons for Altman's firing, leading to a weekend of internal conflict at the company and growing pressure from investors. Altman's removal also triggered the resignation of Greg Brockman, another OpenAI co-founder and former president.

Microsoft, which has invested billions of dollars in OpenAI and has rights to its current technology, quickly moved to hire Altman and Brockman, exacerbating the turmoil at OpenAI. The software giant also pledged to welcome all employees who wanted to follow Altman and Brockman to a new AI research unit at Microsoft.

In recent days, Microsoft had signaled its willingness to support Altman's return to OpenAI, so long as the startup's governance problems were resolved. Microsoft CEO Satya Nadella said in a statement that he was "encouraged by the changes to the OpenAI board" and that he believed it was a "first essential step on a path to more stable, well-informed, and effective governance."

Altman, in his own statement, said that he was "looking forward to returning to OpenAI, and building on our strong partnership with Microsoft" with the new board and Nadella's support.

It is not clear yet if the structure of OpenAI's board will change with its newly appointed members. The company has said that it is "collaborating to figure out the details" and that it thanks everyone for their patience "through this."

Nadella said that Brockman, who was OpenAI's board chairman until Altman's firing, would also have a key role to play in ensuring the group "continues to thrive and build on its mission."

Hours earlier, Brockman returned to social media as if it were business as usual, touting a new feature called ChatGPT Voice that was rolling out to users.

OpenAI's short-lived interim CEO Emmett Shear, the second interim CEO in the days since Altman's ouster, said on social media that he was "deeply pleased by this result" after "72 very intense hours of work."

"Coming into OpenAI, I wasn't sure what the right path would be," Shear wrote. "This was the pathway that maximized safety alongside doing right by all stakeholders involved. I'm glad to have been a part of the solution."