Linda Yaccarino, the chief executive of X and a top lieutenant to its owner, Elon Musk, said on Wednesday that she was leaving the company two years after joining the social media platform.

In a post on X, Ms. Yaccarino, 61, said: “When @elonmusk and I first spoke of his vision for X, I knew it would be the opportunity of a lifetime to carry out the extraordinary mission of this company. I’m immensely grateful to him for entrusting me.”

She did not provide a reason for her departure.

Ms. Yaccarino’s exit caps a tumultuous period at X, which was previously called Twitter and has been remade in Mr. Musk’s image since he bought the platform for $44 billion in 2022. Since then, Mr. Musk has shed three-quarters of the company’s employees, loosened speech restrictions on the platform and wielded X as a political megaphone. Advertisers were at one point spooked by the changes, and the social media company’s ad business declined.

In March, Mr. Musk said he had sold X, which is a privately held company, to xAI, his artificial intelligence start-up, in an unusual arrangement that showed the financial maneuvering inside his business empire. The all-stock deal valued xAI at $80 billion and X at $33 billion, Mr. Musk said. Since then, xAI has been in talks to raise new financing that could value it at as much as $120 billion.

Mr. Musk, who until recently was regularly working in Washington as an adviser to President Trump, has returned to his businesses, which include the electric carmaker Tesla and the rocket company SpaceX. As he and Mr. Trump have tossed criticisms at one another, Mr. Musk has also recently said he was interested in forming a third political party.

Top executives regularly come and go at Mr. Musk’s various companies. One exception is Gwynne Shotwell, the president of SpaceX, who joined Mr. Musk’s rocket company shortly after its founding in 2002.

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