Sunderland have sacked manager Mick McCarthy after three years in charge.
The club are 16 points adrift of safety at the foot of the Premiership and said it was "in the best interests of both parties for him to leave immediately".
Assistant Academy manager Kevin Ball has been put in charge for the last 10 matches of the season with a permanent appointment to be made in the summer.
Chairman Bob Murray said: "I would like to thank Mick McCarthy for his efforts for the club whilst at Sunderland."
The sacking comes the day after Sunderland's 2-1 defeat at Manchester City.
McCarthy said he had given it his best shot and added: "I've enjoyed every single minute of it.
"I'm sure I've got support and I'm sure there are people that think otherwise.
"It's been tough these past few months but it's been a pleasure and I've been fortunate. I've done my best and can't do anything more
"I'll move on and eventually do something else. It's been brilliant and I've thoroughly enjoyed the support of the fans."
Murray added: "We wish him and his family the best for the future."
He said as chairman he took "responsibility for what has proven to be an unsuccessful and heartbreaking season, despite the best intentions, efforts and expectations of every one at the club".
He went on: "I feel deeply sorry that the excitement, optimism and aspirations of all Sunderland fans looking forward to a return to the Premier League have been rewarded in this way and I apologise for this.
"It is especially tough on supporters who have turned out in numbers week in, week out, despite seeing so little to raise their spirits.
"It is hard to see such loyalty unrewarded and I am sorry that performances and results have not mirrored the tremendous level of support that the club has been given.
"The club did not return to the Premiership just to make up the numbers and whilst we fully expected it to be a tough first season back, none of us expected to be in the position we are today.
"Looking ahead we will be taking our time to appoint a successor for what will be another very important season for the club in 2006."
McCarthy took over on 12 March 2003 with Sunderland bottom of the Premiership, taking over from the dismissed Howard Wilkinson who lasted just 27 games.
MICK McCARTHY FACTFILE
Born in Barnsley on 7 Feb 1959
Played 272 games for Barnsley, joined Manchester City for £200,000 in 1983
Republic of Ireland debut in 1984, joined Celtic in 1987
Succeeded Bruce Rioch as Millwall player-manager in March 1991
Appointed Ireland manager in 1996, guided them to last 16 of 2002 World Cup
Appointed Sunderland manager 12 March 2003
After losing out in 2004 play-off finals, guides Sunderland to Championship title in May 2005
McCarthy was powerless to prevent the club, who had already sacked Peter Reid earlier that season, from dropping down to the Championship.
The former Republic of Ireland boss lost all nine games as they finished with a Premiership record low of 19 points.
But despite being saddled with huge debts and having to sell the bulk of his first-team squad, McCarthy led the club to third in the Championship before losing to Crystal Palace in the play-offs.
The following season McCarthy led the club to the Championship title with 94 points.
But this campaign has been a disaster, with the club only winning two games out of 28 games.
They were also knocked out of the FA Cup by League One side Brentford.
McCarthy and Murray had a public falling out when the manager was quoted as saying the club had planned for possible relegation.
The chairman was furious at suggestions that they were not totally committed to keeping the club up, but the pair appeared to patch up their differences.
McCarthy's hopes of keeping them up were hampered by limited funds, with the club's debts at around £40m.
Despite their perilous position the Sunderland players have continued to battle for McCarthy but have been clearly lacking in the quality needed for the top flight.
He leaves with a record of 31 defeats in 37 games in the Premiership.
Ball, a former Sunderland captain, will now take charge for 10 matches but with the club surely already condemned to relegation.
"We have appointed Kevin Ball caretaker manager until the end of the season and hope that supporters will give him their full backing," said Murray.
"Kevin has always felt passionately about Sunderland and is a true professional. His grit, determination and leadership qualities have always been greatly appreciated by Sunderland fans and the club.
"Sunderland supporters have been incredibly tolerant and supportive in the last few months, which have been very difficult, and I would also like to thank them for that.
"Now is the time to give Kevin Ball and the team support to try to get back to winning ways."