London: Emile Smith Rowe freak goal, as Arsenal boosted their hopes of European qualification with their first Premier League to stop Chelsea from moving third in the Premier League, at the Stamford Bridge, here on Wednesday.
Kai Havertz shot over for the hosts early on, before Smith Rowe capitalised on a Jorginho error on 16 minutes.
The midfielder's stray backpass was clawed off the goalline by Kepa Arrizabalaga, but Pierre-Emerick Aubameyang then pounced and cut back for Smith Rowe to finish.
Mason Mount had one shot blocked, and another saved by Bernd Leno, as Chelsea rallied.
After the break, Chelsea substitute Olivier Giroud shot wide while Arsenal's Hector Bellerin forced a save from Kepa.
The Blues nearly snatched a point in stoppage time as Kurt Zouma and Giroud both hit the crossbar in succession, but the Gunners held on.
A first PL double over Chelsea in 17 years lifts Arsenal to eighth on 55 points, one behind Tottenham Hotspur and two adrift of Liverpool.
Chelsea's loss means Thomas Tuchel's side remained fourth and gave renewed hope to chasing teams West Ham and Liverpool, who are hoping to overtake the final Champions League spot.
Chelsea dominated possession on the second half and Christian Pulisic saw a second-half equalizer chalked off for offside after a video assistant referee review. Kurt Zouma and Olivier Giroud then struck the crossbar within mere seconds of each other in the 90th minute as Chelsea wasted a host of chances in a dominant but disjointed performance.
Tuchel made seven changes to keep his players fresh, with Saturday's FA Cup final against Leicester clearly in mind.