Substitute Michael Owen netted a dramatic injury-time winner as United beat City 4-3 in a pulsating Manchester derby at Old Trafford.
Owen replaced Dimitar Berbatov on 78 minutes and struck with a typically cool finish in the sixth minute of injury time to settle a thrilling match in which City had three times come from behind.
Indeed, Craig Bellamy thought he had snatched all three points at the death when he netted his second of the game in the 90th minute, but Owen ensured he will go down in United folklore with an even later strike.
Wayne Rooney had given United the perfect start with the opener after just two minutes only for City to reply through Gareth Barry soon after. A Darren Fletcher brace in the second half twice restored United's lead with Bellamy maintaining City hope with his first in between.
The result sees United move level on points with Chelsea at the top of the table while City's first defeat of the season saw them remain in fourth - at least until Chelsea meet Spurs in the late kick-off.
That Owen managed to steal the headlines says much for the late drama at Old Trafford, given that the day also marked the return of Carlos Tevez to his former stomping ground.
The Argentine managed to shake off a knee injury to start against his former club but amicable scenes in the tunnel which saw Tevez hugging some of his old team-mates quickly disappeared as he was roundly booed on his entrance into the Old Trafford arena.
His every touch was subsequently jeered by those fans for whom he was an idol not so long ago.
But Tevez, who had said he expected to receive a warm welcome on his return, was not diminished by the reception and, almost inevitably, was heavily involved during an explosive first half.
Not only did his hassling and harrying create the chance for Barry to equalise, he was also booked for a late challenge on Rio Ferdinand before hitting an upright before the half-time whistle sounded.
The day started in the worst possible fashion for City as Rooney capitalised on a shocking lapse of concentration in the visitors' defence in just the second minute, firing past Shay Given after the totally unmarked Patrice Evra was allowed to receive a throw-in and find the England striker in the box.
The goal rocked City and with United not giving an inch early on, the pre-match bluster surrounding a shift of power appeared to be nothing more than hot air.
But Mark Hughes's side are undoubtedly a different animal to the one on show last season and they proved as much when they drew back on level terms 14 minutes later, thanks to a combination of a calamitous blunder by Ben Foster and some typical Tevez tenacity.
The England keeper opted against hitting row Z with a clearance, instead choosing to turn back inside his penalty area so he could pick the ball up. But he did not reckon on Tevez, who stole in and dispossessed him before playing the ball across to Barry. The midfielder still had a lot to do, but he coolly found the corner with a first-time strike.
As the opening period wore on, the game settled, but Tevez ensured the excitement was merely on a backburner and it soon reignited when the Argentine hit the woodwork after a careless Rooney backheel allowed Kolo Toure to advance and feed the former United man.
United burst out of the blocks in the second half in a similar vein to how they had in the first and Fletcher restored their lead just four minutes after the restart, rising highest to head home Ryan Giggs's cross.
Soon after Giggs was denied adding another by the legs of Given as the veteran increasingly became a central figure in the game.
But before United could extend their advantage, Bellamy thundered City level for a second time with a stunning strike on 52 minutes that flew into the top corner, leaving Foster no chance at all.
The goal came against the run of play but United did not allow it to derail their form. Indeed they proceeded to dominate the remainder of the second half as should have wrapped up all three points much earlier than they did.
With Giggs pulling the strings, Berbatov in particular was unlucky not to get on the scoresheet. That he did not had much to do with the excellent Shay Given, who twice denied the Bulgarian headers with fine saves.
Given beat a Giggs half-volley behind on 70 minutes, but there was nothing the Irishman could do about Fletcher's second, a near carbon copy of his first, as United took the lead once again.
Still City refused to accept defeat and following an opportunity apiece for Shaun Wright-Phillips and Micah Richards, Bellamy struck with a thunderbolt that stunned the Old Trafford faithful as the visiting support joyfully celebrated.
But those roles were soon reversed as Owen swooped deep into injury time as Hughes was left to bemoan the addition of six minutes of injury time.