The move was confirmed by Kelly’s publicist, Leslee Dart.
Kelly’s departure deprives Fox News of its second-most-watched host, behind only Bill O’Reilly.
In the past two years, Kelly has weathered personal attacks from Donald Trump during his presidential campaign, and last summer she played a behind-the-scenes role in the ouster of Fox News founder Roger Ailes after multiple accusations of sexual harassment.
She is expected to take on a multi-faceted role at NBC.
The move was first reported by The New York Times.