The company's former chief operating officer announced the move in a Facebook post on Wednesday.
She says Meta looks strong and well positioned for the future, making it a good time to step away.
The exit will come when her term ends in May, but she isn't cutting ties altogether.
Sandberg says she will still serve as an adviser to the company.
Meta boss Mark Zuckerberg responded that he looked forward to "a new chapter together".
Sandberg was once his second-in-command, and one of the firm's most prominent faces.
She was the lead architect of Meta's often-criticized ads-based business model.
Over the years she remained a consistent defender of the social network, arguing it was learning from its mistakes, including how to police harmful content.
Before Facebook, Sandberg was a senior executive at Google.
She is also the author of several books, including the 2013 feminist manifesto "Lean In".
