Match Facts Manchester United Manchester United have 71 points, which is already the most the Red Devils have managed across a single season since Sir Alex Ferguson retired.
This latest triumph represents City's third title in seven seasons and Pep Guardiola's seventh league title as a manager.
They have equalled the record for quickest title success held by United's 2000-01 team, winning the league with five games remaining.
West Brom had lost eight of their previous nine games and last won on Jan 13.More news: Israeli security heads confer after Trump's threat to bomb Syria
City did not lose a game until January against Liverpool, and drew just twice until that memorable clash at Anfield, while smashing five past Liverpool at the Etihad early in the season, as they stunned opposition, supporters and critics alike with their performances. The most United can now reach is 86.
Sitting deep and allowing the relegation certainties push forward with the ball was not the type of football expected following United's title-halting comeback against Manchester City last week, but this is not the first time Mourinho has suffered.
That could see Juan Mata recalled while Marcus Rashford may get the nod ahead of Anthony Martial amid rumours both players are becoming unsettled due to a lack of regular starts. West Bromwich Albion West Brom have taken just two points from the last 30 available to them (D2, L8).More news: U.S. & allies launch 'precision strikes' on Syria
If it weren't for Ben Foster in goal, West Brom would have gone into the game at Old Trafford already relegated.
The City manager's decision to forego the match looked justified considering West Brom's awful form, although Jake Livermore's early attempt was a warning shot that undercooked United failed to heed.
But his best moment of the match came to stop Lukaku from opening the scoring after an hour, getting down low to push Lukaku's header wide of the goal and keep his side in the match.
Jay Rodriguez secured rock-bottom West Brom a win at Manchester United that was as remarkable as it had looked unlikely.More news: Beyonce becomes first woman of colour to headline Coachella