The only goal was scored by Jay Rodriguez midway through the second half, to make United pay for their lack of creativity and zest, winning only their fourth match of the season.
"Champions! What a terrific feeling! So happy to be able to share another trophy with our wonderful fans", the 32-year-old Belgian defender said on Twitter.
"City won the title because they won more points than everyone else, they were the best team".
"It hurts [for Manchester City to win the title]".More news: Britain denies Russian claims that it staged Syria chemical attack
Whether Wenger's 22-year reign in charge continues beyond this season now seems to hang on if Arsenal can get past a side that have reached two Champions League finals in the past four seasons. "This is not a dynasty, it is one title we've won".
Realistically it was always a matter of when and not if City would become English champions for a fifth time following a dominant season from the blue half of Manchester. You could see the difference in the attitude of players compared to last week. Jose said we didn't create much in open play because they dominated the ball a lot, you know when you come to Manchester United your work off the ball has to be very good.
Despite Guardiola's men having a 16-point gap at the top of the table, though, Mourinho believes six teams should realistically be challenging for the title.
By winning the title with five matches remaining, City have equalled the English top-flight record (Manchester United in 1907-08 and 2000-01, and Everton in 1984-85 all won the top-flight title with five games to spare).
"We did it! An incredible journey to get here". Congratulations to Manchester City, who are mathematically the Premier League winners.More news: Arab League Summit Slams Iran, Chemical Weapons Use In Syria
It's been a remarkable season for Manchester City who've gone from strength to strength in the Premier League, affirming their dominance since the opening weekend.
"We were masters in complication, everything was complicated", Mourinho told Sky Sports. "Today was a very bad day and we need to move on".
"Football, bloody hell!" Alex Ferguson said with a bemused smile after United capped the most successful season in the club's illustrious history.
While Guardiola said he would be playing golf while the United match took place and a handful of players were reportedly out of the country, captain Kompany was at home watching the drama unfold with his family.More news: Japan, China pledge to work on economic ties amid heightened trade tensions