United won another classic Manchester derby with Robin van Persie's deflected late free-kick handing the Reds a sensational 3-2 triumph after City had fought back from two goals down.
Wayne Rooney's two similar first-half strikes had the Reds on course to end the champions' unbeaten home run in the Barclays Premier League that has lasted almost two years. The match looked to have turned completely with half an hour left as Ashley Young had a goal wrongly ruled out before Yaya Toure netted within seconds.
It allowed the Blues to stage a comeback that led to Pablo Zabaleta levelling from a corner on 86 minutes but the visitors were simply not prepared to settle for remaining three points clear at the top of the table. Incredibly, Van Persie had the final say in stoppage time to end City's proud run and inflict their first league defeat since last April.
There were surprises in both line-ups with Mario Balotelli starting for the hosts while Antonio Valencia and Tom Cleverley were fit enough to represent the Reds. Balotelli had two early chances as City began the better as his ambitious free-kick was helped wide by David De Gea before the Italian could only muster a wild slash at a Gael Clichy centre following a tremendous pass by David Silva.
Sir Alex's side had not threatened before a glorious move on 16 minutes carved open the Blues' defence. Young headed Patrice Evra's ball down the line on to van Persie, whose chest-pass returned it to the winger and had City on the back foot. Young timed it right to feed Rooney and the striker set himself up with a fine touch before scuffing into the far corner past a motionless Joe Hart. It was not the cleanest of strikes but certainly a sweet one.
The way in which United hurt the champions with the first attack of menace was encouraging and captain Vincent Kompany had to come