Arsenal gave rivals Tottenham Hotspur the initiative in the race for top four after losing at home to Brighton.
Prior to the game, the Seagulls had gone seven games without a win and frustrated the Gunners for the most part of the game.
Leandro Trossard gave Brighton the lead after curling his effort past a stretching Aaron Ramsdale.
Arsenal thought they had got their equaliser after Gabriel Martinelli headed home but a lengthy VAR check ruled him offside.
Brighton remained compact and doubled their lead throgh Enoch Mwepu halfway through the second half.
Arsenal rallied on with minutes remaining after Martin Odegaard pulled one back through a deflected shot.
Arsenal remain fifth and are level on points with Spurs, who play later on Saturday against Aston Villa.
