Manager Simon Grayson has parted company with Sunderland, who are 22nd in the Championship after 15 games.
His departure, announced 20 minutes after a 3-3 draw with bottom-of-the-table Bolton Wanderers, comes just four months after he was appointed.
The former Preston North End boss took over at the Stadium of Light in June, replacing David Moyes, who left after the club were relegated.
However, the 47-year-old won just one league game as Sunderland boss.
Chief executive Martin Bain said: “Simon and his team have worked tirelessly to achieve the best for the football club during their time here.
“While we hoped that Simon’s experience in the Football League would help us to a successful season, results have not been good enough for a club of this stature.
“In order for us to improve upon our current position we believe a fundamental change is necessary.”
Grayson’s dismissal makes him the ninth permanent managerial departure from the Wearsiders since Roy Keane’s exit in December 2008.
His is also the shortest tenure.
More to follow.