Erling Haaland secured Manchester City a memorable derby-day triumph as Manchester United failed to capitalise on Phil Foden's sending-off on a day of contentious decisions.
Old Trafford witnessed a pulsating 199th meeting of the Manchester rivals as Enzo Maresca's new-look side won the first clash between the sides since Pep Guardiola's departure.
Much has changed at City this summer but Haaland remains a familiar foe, with the striker's ninth Premier League goal against United taking him clear as top scorer in this fixture and sealing a 1-0 victory.
But the main subject of debate after Sunday's game will be the decisions to send off Foden and award the City sharpshooter's winner.
The visitors had felt aggrieved when Foden was sent off in the 23rd minute for petulantly reacting to a Bruno Fernandes kick.
Marcus Rashford and Kobbie Mainoo hit the woodwork but United could not make the most of their man advantage, with the VAR's decision to overturn an initial offside call against Haaland causing anger and confusion.
Gianluigi Donnarumma made a crucial stoppage-time save from Bryan Mbeumo to secure a dramatic win that Maresca celebrated by charging towards the City fans at full-time.