United had the opportunity to prolong City's wait to secure title glory by another week when they took on West Brom this afternoon.
Jay Rodriguez's second-half victor meant City securing the league title with five games to spare.
Here's what pundits, managers and players have said after City won the league...
What we have done was not realistic so they deserve all my respect. They've been by far the best team in the league. Everything was complicated. Players didn't want to or didn't play simple. It's good for the Premier League as well.
United's performance was in stark contrast to their display against City last time out, and Mourinho's team selection is also likely to come under scrutiny. I believe in myself. A 16-point lead with five games to play and 93 goals scored represents an emphatic response, not that any doubts ever existed inside the City dressing room.
"We were masters in complication, everything was complicated", Mourinho added.
"This is not a dynasty, it is one title we've won".
"Probably because I won eight championships I was not on the moon with the victory against them because that doesn't make me feel super-happy". I have never been able to retain a title and I want to see if this team has got it to carry on and be even more successful.
A week after an inspiring comeback win against Manchester City, Manchester United fell to a 1-0 defeat at Old Trafford against bottom club West Bromwich Albion on Sunday and manager Jose Mourinho said such inconsistency needed to change if they were to challenge their neighbours next season.
Manchester City won the title because they won more points than anybody else. because during the season they only lost two matches. We lost the game because they were better. That's the reason why they were champions.
Manchester City midfielder Kevin De Bruyne on Twitter: Unbelievable season for us. But we have a second chance against Swansea and we're going to try and be champions. City have elevated the level of the football. It is possible to win the league that way.