Marko Arnautovic struck the winner as West Ham beat Chelsea 1-0 at the London Stadium to record their first Premier League win since September.
West Ham got off to a fine start, opening the scoring inside six minutes through Arnautovic, who played a one-two with Manuel Lanzini on the edge of the box before curling an excellent strike into the bottom corner.
Chelsea spent much of the rest of the first half searching for an equaliser and came closest just before the half-hour mark, with N'Golo Kante bringing out a save from Adrian with a strike from distance, before the West Ham keeper pulled off another stop to deny Davide Zappacosta a few moments later.
The visitors, who threw on Pedro Rodriguez for Tiemoue Bakayokot at half-time, went close again through Zappacosta near the hour-mark, but his effort bent just wide of the target.
Chelsea continued to pile on the pressure as the game wore on, with Alvaro Morata and Eden Hazard firing wide in the closing stages, but West Ham were able to hold on for the three points.