The leaders moved an insurmountable 16 points clear of United with five matches remaining, thanks to Jay Rodriguez's late strike at Old Trafford.
Pep Guardiola becomes the third Man City manager to claim the Premier League title, after Roberto Mancini, in 2011/12, and Manuel Pellegrini, in 2013/14.
City have dominated this season, racking up 87 points with a goal difference of +68, after winning 28, drawing three and losing just two of their 33 fixtures so far.
They are eight points adrift of the Premier League record for points in a season, Chelsea's 95 in 2004/05, and can become the first team to break the 100-point barrier, with a total of 102 possible from their remaining five fixtures.
The League high of 30 wins in a campaign, earned by Antonio Conte's Chelsea last season, is also in City's sights.