Antonio Conte’s men handed the Portuguese his heaviest defeat in the Premier League to move up to fourth in the table and a third straight victory.
Goals from Pedro, Gary Cahill, Eden Hazard and N’Golo Kante secured the three points for the Blues.
Chelsea took the lead just after 30 seconds when Pedro capitalised on slack defending to hand United their quickest goal in the Premier League this season.
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Gary Cahill extended the Blues’ advantage midway through the first half after the visitors allowed Eden Hazard’s corner to bounce in their box.
United’s woes were compounded in the second half as Hazard drilled in a precise 15-yard strike, before N’Golo Kante completed the scoring with his first goal for the club, latching on to a Pedro flick and finishing marvellously.
The result represents the heaviest defeat for Jose Mourinho in all competitions since Real Madrid’s 5-0 defeat by Barcelona in November 2010.
The win lifted the Blues above Tottenham into fourth, while United stay seventh on the log, six points behind leaders Manchester City.
Meanwhile, Nigeria striker, Kelechi Iheanacho, saved Pep Guardiola’s blushes as he came off the bench to score for Manchester City in their 1-1 draw with Southampton at the Etihad Stadium on Sunday, taking the Citizens to the top of the log on goal difference.