Outplayed by a revitalised Aston Villa for the first half and the early part of the second, United drew on all their inner strength for a dramatic finale in which Federico Macheda was the unlikely hero.
With the score 2-2 and the game three minutes into five minutes of stoppage time, veteran Ryan Giggs found the 17-year-old Italian inside the Villa box.
Macheda, the leading scorer for both United's reserve and Academy sides, turned Villa centre-back Curtis Davies 12 yards out and hit the sweetest of curling right-foot shots beyond goalkeeper Brad Friedel and into the far corner of the net.
United went wild while Villa stared in disbelief at the points which had been so dramatically grabbed from their grasp.
The result put United back on top of the Premier League - a point above second-placed Liverpool with a game in hand.
It could prove to be the defining moment of the season, yet this was one of the biggest smash-and-grab raids in the Premier League so far during the current campaign.
United were dreadful in the first half. Without Wayne Rooney, Dimitar Berbatov, Paul Scholes, Rio Ferdinand and Nemanja Vidic - all missing for a variety of reasons - they looked like a ship without an anchor. The absence of Ferdinand and Vidic in particular being most noticeable as the defence was a shambles.
United should have been behind in the fourth minute. John Carew was unchallenged as he met Ashley Young's corner, only to see his near post header from six yards cleared off the line by Darren Fletcher via a post.
United took the lead against the run of play in the 14th minute.
James Milner's hurried back-pass was scooped up by Friedel ten yards from goal on the left side of the Villa box. Referee Mike Riley awarded United a free-kick which Giggs tapped to Cristiano Ronaldo and United's leading scorer made it 14 Premier League goals when he sent his right-foot shot crashing into the roof of the net.
Villa kept their cool and their pressure paid off on the half-hour. Gareth Barry's cross from the right saw Carew again unchallenged in the centre of the United penalty area to head the ball beyond goalkeeper Edwin van der Sar and into the net from ten yards.
Villa were deservedly ahead after 58 minutes. Carew turned goal-maker when his left-wing cross was headed in from six yards at the far post by the unmarked Gabriel Agbonlahor.
Macheda replaced the ineffective Nani in the 61st minute to make his senior debut and United began to slowly come to life.
Villa seemed to sit back and United came at them. In the 80th minute, Villa failed to clear Gary Neville's cross from the right. Michael Carrick touched the ball back to Ronaldo who scored with a clever left-foot shot from just outside the Villa box.
The pressure was turned up several degrees in the closing minutes. Friedel produced superb saves to deny Fletcher and substitute Danny Welbeck, but it was the fantastic Federico who had the last laugh.