Pep Guardiola’s side also ended United’s 40-match unbeaten run at home – which stretched back to the win in September 2016 – to strike a potentially decisive blow against its closest rivals in the title race.
City took the deserved lead when man-of-the-match David Silva hooked home from close range after confusion at a corner on 42 minutes, only for United to be handed a lifeline in first-half stoppage time when poor defending from Nicolas Otamendi and Fabian Delph allowed Marcus Rashford to steal in for a composed finish.
Otamendi made amends nine minutes after the break when Romelu Lukaku – who had a nightmare game – lashed at a clearance in the area and the City defender pounced on the rebound to score.
City, who have dropped only two points in their first 16 games, had opportunities to extend their lead but it was keeper Ederson who made the decisive late intervention with a miraculous double late save from the luckless Lukaku and substitute Juan Mata.
Guardiola’s side become the first team to win 14 successive Premier League games in a single season, also levelling Arsenal’s outright top-flight record, set between between February and August 2002.
It is a brave call to declare the Premier League title race over in early December – but the statistics and evidence is piling up to suggest the chase is on for second place behind Manchester City.
City will effectively have to lose four games while all of their rivals need to keep winning, tough to see with Guardiola’s team having won every league match since Everton took a point at Etihad Stadium in the second game of the season.
The trip to Old Trafford, and the renewal of old rivalries between Guardiola and Mourinho, was the most eagerly awaited game of the season between the two teams at the top of the table and was seen as the acid test of City’s apparent infallibility.
And those looking for cracks in the Guardiola armour pointed to City having to secure three wins against Huddersfield Town, Southampton and West Ham United with late, late goals in their most recent league games.
If City’s confidence had been shaken at all by having to fight for victories, there was no sign here as they played with a composure and positivity that was a level above Mourinho’s Manchester United.
They needed Ederson’s late heroics but there can be no doubt they were deserved winners and even showed the street-wisdom of champions to run down the clock in the closing seconds, to the fury and frustration of Old Trafford.
The Premier League title race may not be over – but there was no escaping the feeling that a crucial blow has been inflicted on United and the rest of Manchester City’s pursuers.