Roberto Mancini's men scored twice in added time to beat QPR 3-2 and win their first title since 1968 on a day of incredible drama in the Premier League
Roberto Mancini's men led at half-time when Rs' goalkeeper Paddy Kenny failed to stop Pablo Zabaleta's snap-shot from six yards after 39 minutes.
But, with Mark Hughes' side camped inside their own half for the majority, Djibril Cisse pounced on a mistake by Joleon Lescott to hammer an equaliser past Joe Hart.
City appeared to be handed the upperhand when Rs' captain Joey Barton was sent off just before the hour mark for striking Carlos Tevez, only for QPR to go in front when second-half substitute Armand Traore stormed down the left flank and delivered a whipped cross for Jamie Mackie to head into the net.
As the game entered stoppage time, Edin Dzeko lost his marker at a corner to equalise, with Sergio Aguero scoring the most dramatic of winners with just one minute of playing time remaining.
A first-half Wayne Rooney header was enough for the Red Devils to claim the three points needed over Sunderland, but Sir Alex Ferguson's side needed Manchester City to slip up against QPR if they were to claim their 20th league title.
Speaking after the game, Roberto Mancini told Sky Sports: "Football is incredible.
"This is for our supporters, they deserved this.
"To win like this is incredible. I've never seen a final day like this. We didn't deserve to lose this game. We had a lot of chances. We deserve to win this championship.
"After 44 years, for all our supporters it's incredible. It's been a crazy season."