Match ends, Manchester City 2, Manchester United 3.
Manchester City must wait to secure the Premier League title after Manchester United mounted a remarkable second-half derby fightback to come from two goals down to win at Etihad Stadium.
City needed victory to be confirmed as champions but Paul Pogba scored two goals in two minutes to overturn City's first-half lead before Chris Smalling's volley completed the dramatic turnaround.
Pep Guardiola's side had delivered a first-half masterclass with captain Vincent Kompany scoring with a thumping header after 25 minutes and Ilkay Gudogan adding a second five minutes later after a clever turn and finish.
Outclassed United remained in contention after Raheem Sterling skied two golden chances over the bar with the goal at his mercy and Gundogan headed straight at keeper David de Gea when unmarked eight yards out.
It gave United hope and how Jose Mourinho's team responded as Pogba - out of sorts at Old Trafford recently and at the centre of claims by Guardiola before the game that he had been offered to City in January - stole in to pull a goal back after 53 minutes and head the equaliser two minutes later.
The remarkable turnaround was complete when Smalling, badly at fault for Kompany's goal, arrived unmarked to steer Alexis Sanchez's free-kick past the exposed Ederson in the 69th minute.
In a furious finale, players from both sides clashed and Ashley Young was fortunate that his wild lunge on City substitute Sergio Aguero in the area was ignored by referee Martin Atkinson.
De Gea made a world-class one-handed save from Aguero as City attacked furiously - but United held out and Guardiola's title party must wait for another day.
City will win the title next weekend if they beat Tottenham at Wembley on the Saturday (19:45 BST kick-off) and United lose at home to bottom club West Brom on Sunday (16:00).
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City collapse puts title party on hold
When Gundogan turned sweetly and poked a right-foot finish beyond De Gea after half an hour, the champagne was being placed on ice by Manchester City's supporters - and on the evidence up to that point no-one could blame them.
City were tearing United's fragile defence apart and Gundogan's goal was a fitting return for domination that had already brought them the lead through Kompany's header.
It was hard to see how the visitors, so passive and pedestrian, could do anything other than mount a damage-limitation exercise before City's title celebrations got under way.
And then came what proved to be the decisive passage of play when Sterling sent two easy chances wildly over the top and Gundogan provided a tame headed finish to another great opportunity.
It left the door ajar for United - and they burst through it once manager Jose Mourinho had delivered his half-time message.
When Pogba slipped through eight minutes after the interval to beat Ederson and give United hope, the defensive demons that put the skids under City in the Champions League quarter-final first leg at Liverpool on Wednesday surfaced once more.
Nicolas Otamendi, so solid and improved before that 3-0 loss, lost Pogba in the area as he headed home to restore parity in the space of two minutes, and City's defenders were once again caught off-guard when Smalling was left totally unmarked to turn in Alexis Sanchez's free-kick after 69 minutes.
City were stunned - flaws exposed. Pep Guardiola's side conceded three in 19 minutes at Anfield and three in 16 minutes here. Lightning had struck twice in the space of four days.
It was only the brilliance of De Gea, with a world-class save from substitute Aguero, that stopped City rescuing the respectability of a point - but there was a serious sense of anti-climax around the Etihad at the final whistle.
City felt they were on the wrong end of several decisions from referee Martin Atkinson, particularly when Young clearly followed through on Aguero in the area in the second half, but they only have themselves to blame after the failure to take those first half chances and that second-half defensive collapse.
Indeed, one City supporter - and not a child either - was in tears in his seat in the stand. He will cheer up when the title formalities are complete, but this was a bitter pill to swallow for Guardiola, his team and their fans.
Pogba raises game to lift United
Pogba's first-half performance aroused comment for two reasons - the manner in which he was outmanoeuvred in midfield and a hair colour that looked suspiciously like an unwitting title tribute to Manchester City with its flashes of blue.
The man Guardiola claimed was offered to Manchester City in January was as off the pace as his team-mates and social media would not have made pleasant reading for the France playmaker.
But how it all turned in the space of two minutes early in the second half as the tall, long-striding Pogba flipped the game on its head and opened up the possibility of a United victory that seemed light years away at half-time.
And what resolve Mourinho's side showed to dig their way out of the hole they found themselves in after 45 minutes, stirring themselves for a comeback that will at least give them pride that they did not allow City to have their title celebration at their expense.
True, they rode their luck as Young somehow escaped punishment for that reckless challenge on Aguero in the area, but they scrapped it out and relished the feisty later exchanges when City's discipline deserted them.
This will not stop City winning the title but it will give United a real sense of satisfaction in a season where they have been comprehensively overshadowed by their neighbours.
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Can City pick themselves up for Champions League?
Liverpool, who come to the Etihad protecting that 3-0 lead in the Champions League quarter-final second leg on Tuesday, will have watched events unfolding here with mixed emotions.
In the first half, City looked every inch a side with the capability to overturn that deficit as they dazzled in attack and left United chasing shadows in midfield.
In the second, they looked like a team who would be easy prey for Liverpool's goalscoring triumvirate of Sadio Mane, Roberto Firmino and, if fit, Mohamed Salah.
City's performance was two-faced and Guardiola will know that just one piece of the frailty they have demonstrated in conceding six goals in their past two games will be fatal against the Reds' potent attack.
Guardiola will also know City must sustain the level of the first half for 90 minutes and eradicate the errors of the second or their Champions League campaign will be over.
Man of the match - Paul Pogba (Manchester United)
'Can we improve enough next season?'
Manchester United manager Jose Mourinho speaking to Sky Sports: "We moved the ball more than any team has against Manchester City. We pressed a bit higher and we kept the shape to get a good result.
"I think mathematically we need six points to stay in the top four and this win is part of that.
"Our challenge is to finish second but I want to congratulate City for the title - because they are going to win and deservedly. They gave no chance to the others because they had this season of not stopping winning.
"My objective here was to get points and not spoil any celebrations. The point is can we improve enough to catch them next season?"
Manchester City manager Pep Guardiola speaking to BBC Sport: "To concede three goals against a very good team is tough.
"We were the team that conceded the least goals. United created four chances, which isn't too much. How many chances did we create? Much, much, more. But you have to put the ball in the net."
United's comeback kings - the best of the stats
- City lost a Premier League game they were winning by a two-goal margin for the first time since October 2008.
- United have won nine Premier League away games when trailing by at least two goals - four more than any other side in the competition.
- This was the first time a side managed by Pep Guardiola has conceded at least three goals in consecutive games in all competitions, having lost 3-0 to Liverpool in the Champions League on Wednesday.
- Guardiola lost a game in which his side was winning by a two-goal margin for the first time since December 2013, when his Bayern Munich side lost 3-2 to Manchester City.
- Both Smalling and Pogba have won all nine Premier League games in which they have scored - only former Liverpool forward Ryan Babel has a better 100% record in the competition (11/11).
- There were just 97 seconds between Pogba's first and second goals.
- United forward Alexis Sanchez has provided two assists in a Premier League game for only the second time, also doing so against Newcastle in December 2014.
- Sanchez has had a hand in four goals in his past two Premier League games for Manchester United (one goal, three assists).
Manchester City welcome Liverpool for the second leg of their Champions League quarter-final on Tuesday (19:45 BST kick-off) before travelling to Wembley to take on Tottenham in the Premier league on Saturday (19:45).
Manchester United host bottom side West Brom to Old Trafford in the league next Sunday (16:00).
- 3DaniloBooked at 90mins
- 4KompanyBooked at 90mins
- 8GündoganSubstituted forAgüeroat 76'minutesBooked at 79mins
- 25FernandinhoBooked at 79mins
- 21SilvaSubstituted forDe Bruyneat 72'minutes
- 20Bernardo SilvaSubstituted forGabriel Jesusat 72'minutesBooked at 90mins
- 7SterlingBooked at 63mins
- 17De Bruyne
- 33Gabriel Jesus
- 42Y Touré
- 1de Gea
- 25A Valencia
- 21HerreraBooked at 37minsSubstituted forLindelöfat 90+4'minutes
- 6PogbaBooked at 81mins
- 14LingardSubstituted forMcTominayat 85'minutes
- 9LukakuBooked at 45mins
- 7SánchezSubstituted forRashfordat 82'minutes
- 40Castro Pereira
- Martin Atkinson
- Shots on Target
Second Half ends, Manchester City 2, Manchester United 3.
Attempt missed. Vincent Kompany (Manchester City) left footed shot from the centre of the box is high and wide to the left. Assisted by Kevin De Bruyne with a cross.
Substitution, Manchester United. Victor Lindelöf replaces Ander Herrera.
Corner, Manchester United. Conceded by Leroy Sané.
Gabriel Jesus (Manchester City) is shown the yellow card for a bad foul.
Foul by Gabriel Jesus (Manchester City).
Ander Herrera (Manchester United) wins a free kick on the right wing.
Vincent Kompany (Manchester City) is shown the yellow card.
Foul by Gabriel Jesus (Manchester City).
Ander Herrera (Manchester United) wins a free kick on the right wing.
Danilo (Manchester City) is shown the yellow card for a bad foul.
Foul by Danilo (Manchester City).
Marcus Rashford (Manchester United) wins a free kick on the left wing.
Corner, Manchester City. Conceded by Romelu Lukaku.
Raheem Sterling (Manchester City) hits the right post with a left footed shot from very close range. Assisted by Nicolás Otamendi following a corner.
Attempt blocked. Nicolás Otamendi (Manchester City) right footed shot from the centre of the box is blocked. Assisted by Kevin De Bruyne with a cross.
Corner, Manchester City. Conceded by Nemanja Matic.
Attempt blocked. Fernandinho (Manchester City) right footed shot from the centre of the box is blocked. Assisted by Kevin De Bruyne with a cross.
Corner, Manchester City. Conceded by Chris Smalling.