Chelsea 2 Arsenal 4
Chelsea were guilty of more woeful defending at Stamford Bridge, where they suffered another dismal defeat.
Timo Werner hauled them level soon after Eddie Nketiah’s early opener and, after Emile Smith Rowe restored Arsenal’s lead, Cesar Azpilicueta equalised just after the half-hour mark.
But Nketiah struck again in the second half and Bukayo Saka’s stoppage-time sealed victory for the Gunners.
Chelsea, beaten by Real Madrid and thrashed by Brentford in their previous two matches at the Bridge, have now conceded 11 goals in three home games.
Nketiah put Arsenal ahead by pouncing on a weak header from Andeas Christensen, who was substituted at half-time.
Werner’s deflected effort cancelled out that lead but Smith Rowe’s classy finish after being set up Saka put Arsenal back in front.
Chelsea responded again, this time through Azpilicueta, but Nketiah helped himself to another goal after a flurry of mistakes as the Blues failed to clear their lines.
And Saka rubbed salt in Chelsea’s wounds by scoring from the spot after being fouled by Azpilicueta.
Romelu Lukaku started for the hosts and was poor again. It was a night to forget for Thomas Tuchel’s side.