Louis van Gaal has been sacked as manager of Manchester United, with former Chelsea boss Jose Mourinho set to be named as his replacement.
Van Gaal leaves after two years of a three-year contract, having discussed severance terms on Monday.
The former Netherlands boss, 64, is believed to earn around £6.4m a year.
Mourinho's appointment is expected to be confirmed after the 53-year-old Portuguese meets senior United officials on Tuesday.
Manchester United confirmed Van Gaal's departure at 20:30 BST, praising his "great professionalism and dignity throughout", while adding "a decision on a successor as manager will be announced soon".
In a separate club statement released at the same time, Van Gaal said he was "very disappointed" not to see out his "intended three-year plan".
United have made an offer to Ryan Giggs, Van Gaal's assistant, for him to stay at Old Trafford, but it is not known what role he would have and whether he would accept.
BBC Sport reported on Saturday that United's FA Cup win over Crystal Palace would be Van Gaal's last game in charge.
He arrived at Manchester United's training ground at 08:45 BST on Monday and left shortly before 17:00.
Forty-five minutes after his arrival in the morning, League Managers Association lawyer Paul Gilroy QC also drove into Carrington.
Gilroy is the same employment barrister who acted for David Moyes when he was sacked as manager by United in 2014.
He arrived at about 09:30 and was initially refused entry before being allowed in about 15 minutes later, refusing to answer questions about the reason for his presence.
According to his profile page on the Nine St John Street Chambers website, Gilroy has advised and acted for a number of football clients, including Roy Hodgson, Martin O'Neill, Sir Alex Ferguson, Harry Redknapp, Roy Keane, Roberto Martinez, Sam Allardyce, Brendan Rodgers, Alan Pardew, Nigel Pearson and Steve McClaren.
Van Gaal took control of United after leading the Netherlands to the semi-finals of the 2014 World Cup in Brazil.
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The Old Trafford club finished fourth in the Premier League in his first season in charge to qualify for the Champions League.
But they finished fifth this term and will play in the Europa League next season.
They only scored 49 league goals - their lowest total since 1989-90.
Saturday's FA Cup success at Wembley gave United a first trophy since Sir Alex Ferguson won the Premier League in 2013 in his last season before retirement, but it was not enough to stop Van Gaal from losing his job.
Mourinho was sacked by Chelsea last December, just seven months after leading the London club to the Premier League title.
Gary Lineker tweeted: "Crikey! Manchester United have sacked Louis van Gaal. Who saw that coming? Next thing you know they'll appoint Jose Mourinho."
The Match of the Day presenter and former England striker added: "One thing is for sure, Mourinho is a brilliant coach and a winner. As close as you could ever get in football to guaranteeing success."
Former Dutch player, Ronald de Boer, who played under Van Gaal at Ajax and Barcelona, told BBC Radio 5 live: "He should retire and enjoy his life. He does not have anything to prove to the football world as he has an unbelievable amount of trophies and has respect from a lot of players and managers."
Ian Sterling, chairman of Manchester United Supporters Trust, said: "Van Gaal's fate was sealed with his results over the season. The style of play and football has been the worst I have seen in my time following United. A positive is that the club has acted quickly and a new manager will be in place in preparation for next season.
"The club has acted in the best possible way for its own interest and Van Gaal has been a victim of that. The supporters wanted a change, to put someone in charge who knows the philosophy of the club. Attacking and competing football rather than the game of chess we have seen this season.
"For many other clubs, winning the FA Cup would be a springboard to next season, for us it has been a finale. Mourinho is a 'Marmite' manager, you either love him or hate him. He finished on a failure at Chelsea so maybe he has to come here and prove himself again.
"All the Manchester United fans want is someone who respects what the club is about. My concern is that he plays a similar style to Van Gaal. If Mourinho comes here and loves United more than himself, he will be a success."
Meanwhile, 52.8% of thousands of Sportsday readers said Mourinho was not the right man for Manchester United, while only 20% of a separate vote said they would be Premier League champions next season.
Former Chelsea winger Pat Nevin told BBC World Service: "Van Gaal will be upset, but when time passes and he has time to look back on his career. he walks out of Manchester United after winning a major trophy. Maybe it wasn't the worst time to go after all."
On Mourinho, Nevin added: "Nobody but nobody in world football brings in the trophies like Jose Mourinho.
"It's not heart. This is head. If it was heart I don't actually think it would have been Jose Mourinho.
"I think it would have been Ryan Giggs or maybe another ex-Manchester United player. There were a lot of other possible candidates out there. This is the head ruling here. They had to go and get the man who could do the best job.
"Was Alex Ferguson the easiest man to work with all the time? What did he give you? Success. Hence, Manchester United almost, to some degree, had to go down this route.
"He will do what he knows succeeds and it's much, much easier to win with tried and tested players who have been there and done that.
"In reality, he will bring in tried and trusted players from all around the continent for a lot of money."
BBC sports editor Dan Roan:
"In April 2014, United's mishandling of the sacking of Moyes was heavily criticised, the coach humiliated when learning of his demise through the media.
"The club's hierarchy accepted it was wrong that news had leaked out before the manager had been informed. But two years on, it has happened again.
"Van Gaal was apparently informed of his impending departure by his wife when - still at Wembley following the club's FA Cup final win - she read the news on the BBC website on Saturday evening.
"United hold the Dutchman in high regard and had desperately tried to maintain secrecy during their negotiations with Mourinho, hoping Van Gaal would lead his team to a top-four spot in the Premier League.
"Even after that target was missed, the club wanted him to be able to enjoy his FA Cup win, never once briefing against their coach or adding to the speculation. But it was always naive to think that news of their plans would remain secret.
"Once the news broke on Saturday, it was hard to fathom why they waited to put Van Gaal out of his misery. Once again serious questions will be asked about the way the Glazer regime runs the club - and the way it communicates."
"It does not help of course that the club has absent, silent owners in the Glazers - and a barely-visible executive vice-chairman in Ed Woodward."
"The laboured departure of Van Gaal feels like a watershed moment for United. The period since Sir Alex Ferguson left has been characterised by continued commercial success, but - more importantly for the fans - a drastic slump in on-field performance, near-misses in the transfer market, and two failed managerial appointments.
"The arrival of the highly controversial but serially successful Mourinho is symbolic of an acceptance that things must now change, and that winning is the priority. But it also represents an admission that the three years since Sir Alex Ferguson stepped down have not gone according to plan."
BBC Sport's chief football writer Phil McNulty:
"While United's handling of his departure can be criticised, there is no doubt it is the right decision after a joyless period in Old Trafford history.
"The 64-year-old failed to live up to his billing as an innovative, attacking coach who would blow away the cobwebs of the Moyes era.
"Van Gaal presided over quite the opposite, namely a staid and rigid United side whose football was boring and functional.
"The loss of Champions League status next season, despite the FA Cup win, was the final straw and it is hard to imagine his departure will be mourned by many United fans. His reign that will not live long in the memory."
How do the stats shape up?
- Manchester United scored 49 Premier League goals this season - one more than Blackburn scored when they were relegated in 2012
- For the second consecutive season, United ended up with a negative goal difference away from home
- They went 11 home games without scoring a first-half goal earlier this season
- They conceded the joint-fewest goals in the league - 35 - along with Tottenham
- The team made 3,222 backwards passes - the most in the league
- Van Gaal used 33 players over the season - the second highest number after Liverpool (34)
- United topped the clean sheet record table alongside Arsenal with 18
What is his legacy?
Van Gaal arrived at Old Trafford with his reputation enhanced after steering the Netherlands to the 2014 World Cup semi-finals.
The experience he gained while managing Ajax, Barcelona and Bayern Munich also suggested he had the necessary clout and ego to succeed at Old Trafford, in contrast to predecessor Moyes, who had been in charge at Preston and Everton before taking over when Ferguson retired.
After a solid first season, Van Gaal was expected to turn United into title contenders, especially after taking the club's outlay on players to more than £250m since the summer of 2014.
His record in the transfer market has been hit and miss. Angel di Maria - a British record signing at £59.7m - faded after a fast start and was sold, while Radamel Falcao delivered little after his loan move from Monaco.
The summer of 2015 has hardly proved a success either, with Bastian Schweinsteiger and Morgan Schneiderlin, who reportedly cost United a combined total of around £40m, failing to add dynamism to midfield.
This campaign has also been undermined by injuries, with Luke Shaw, Antonio Valencia, Marcus Rojo, Schweinsteiger, Wayne Rooney, Michael Carrick, Phil Jones and Ashley Young all missing significant parts of the season.
However, Van Gaal has given debuts to 14 academy graduates including midfielder Jesse Lingard, who scored the winner in the FA Cup final against Crystal Palace and striker Marcus Rashford, who has netted eight goals since making his debut in February, earning a call-up to the England national team.
What did his critics say?
A number of significant former United players have taken issue with the style of play under Van Gaal, claiming his tactics are negative and players are afraid to express themselves.
"Manchester United are going backwards again and I don't see that changing because the manager will not change [his tactics]," said Rio Ferdinand, the England defender signed for a then British record £30m in 2002.
Steve Coppell, who starred for United in the 1970s and 80s, said it was hard to understand Van Gaal's philosophy, claiming "players sometimes do not really understand what he's trying to get through to them".
Former midfielder Paul Scholes - a member of the club's legendary 'Class of '92' - was one of the Dutchman's harshest critics.
"It seems he doesn't want players to beat men and score goals," he said. "It's not a team I would have enjoyed playing in. "There's no spirit, there's nobody having a go at each other, there's no smiling, there's no entertainment."
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