At the Emirates Stadium, three second-half goals handed Brighton a commanding 3-0 victory.
The Gunners had a difficult afternoon, which started when Gabriel Martinelli left the game hurt after 20 minutes.
replacing him Just after the halfway point, Leandro Trossard came close to giving Arsenal the lead, but his shot hit the crossbar.
Julio Enciso headed in from close range after Pervis Estupinan bounced the ball back into the area, giving Brighton the vital advantage six minutes into the second half.
In the final four minutes, Brighton added a second goal. Deniz Undav, a replacement, expertly lifted the ball past Aaron Ramsdale to score after Trossard’s attempted flick ricocheted off Pascal Gross.
In the sixth minute of stoppage time, Estupinan added a third goal to seal Brighton’s fourth victory in their past five trips to the Emirates Stadium and only Arsenal’s second home loss of the year. Undav’s original shot had been stopped when Estupinan reacted quickest to score.
Brighton rises to sixth place with 58 points.