Two goals from Granit Xhaka and Peirre-Emerick Aubameyang saw Manchester United suffer their first Premier League defeat to Arsenal under the care of Ole Gunnar Solskjaer.
Switzerland midfielder Grani Xhaka opened scoring for Arsenal in the 12th minute shooting past David De Gea from outside the penalty area.
Manchester United had clear chances to score when things were goalless but Romelu Lukaku hit the bar and Brazilian Fred struck the bar for United.
Bernd Leno of Arsenal cleared two crucial balls from Romelu Lukaku before Aubameyang doubled the lead in the 69th minute when Fred fouled Alexandre Lacazette.
Arsenal win sends them above Manchester United and a point behind third placed Tottenham who were beaten by Southampton on Saturday.
The race for a Champions League spot has now become tighter as the gap between Tottenham, Arsenal and Manchester United being so close.
Arsenal football turn around
Arsenal changed its football style with Aubameyang becoming more clinical in the penalty spot unlike the clash with Tottenham.
Having been beaten over the week by Rennes, Arsenal made six changes in its squad ruling out any chances of fatigue.