Newcastle's managing director Lee Charnley has left the club after seven years in the role.
Charnley, who has been with the club for 22 years, completed a handover period with the new Saudia Arabia-backed owners following their takeover.
Newcastle have begun a formal recruitment process to appoint a new CEO.
"The club, its people and our city will always be very special to me," said Charnley.
Amanda Staveley and fellow owners, the Reuben brothers and Saudi Arabia's Public Investment Fund, bought out Mike Ashley in a deal worth £305m six weeks ago.
Charnley added: "To have been at Newcastle United for 22 years has been an honour and a privilege.