Arthur Masuaku’s first Premier League goal ended Chelsea’s eight-match unbeaten run as West Ham United earned a dramatic 3-2 win at the London Stadium.
West Ham, who also scored three times against Liverpool last month, turned this match around after trailing twice to Chelsea, who also conceded more than once for the first time this season.
Thiago Silva headed in Mason Mount’s corner on 28 minutes but West Ham levelled 12 minutes later when Edouard Mendy brought down Jarrod Bowen after Jorginho's underhit backpass. Manuel Lanzini converted from the spot.
Chelsea went back in front before half-time through Mount’s spectacular volley.
Bowen brought West Ham level again on 56 minutes with a curling shot from outside the area.
Substitute Masuaku won the match in the 87th minute when his cross-cum-shot caught out Mendy at his near post.
Chelsea drop to third on 33 points after Liverpool and Manchester City went above them by beating Wolverhampton Wanderers and Watford respectively later in the day.
West Ham stay fourth on 27 points.
West Ham: 12 Dec v Burnley (A)
Chelsea: 11 Dec v Leeds (H)
Referee: Andre Marriner. Assistants: Simon Long, Richard West. Fourth official: Andy Madley. VAR: Darren England. Assistant VAR: Simon Bennett.