It was United's heaviest ever home defeat in the Premier League as their neighbours romped to a sensational victory.
Mario Balotelli put the visitors in front on 22 minutes and added a second on the hour after Jonny Evans had been sent off for a professional foul two minutes into the second half.
Sergio Aguero added a third on 69 minutes and although Darren Fletcher pulled one back nine minutes from time, City scored three times in the closing minutes. Edin Dzeko got two and David Silva one to inflict United's first defeat of the season and their heaviest at home since 1955. For an in-depth match report, click here.