Olivier Giroud and Mesut Ozil scored late goals as Arsenal ended Group F leaders Bayern Munich's 12-match winning run in all competitions with a 2-0 victory in the Champions League clash at the Emirates Stadium.
Arsene Wenger insisted before the match that his side were capable of beating Bayern and the hosts had the best chances early on, with Ozil being denied by his compatriot Manuel Neuer.
The German champions began to find their way into the match, however, and they forced Petr Cech into a smart save on his first European start for Arsenal when Thiago exchanged passes with Thomas Muller and drilled a powerful effort towards goal.
Douglas Costa, restored to the Bayern side, had threatened the home defence in the early stages and his footwork beat Hector Bellerin before Cech parried his effort away at the near post as the visitors began to show their quality.
Pep Guardiola's side had won their previous 12 matches in all competitions and they continued to pin the hosts back in their own half, but they were denied again by Cech when Xabi Alonso found Arturo Vidal on the edge of the box.
With an opening goal for the visitors seeming likely, it was Arsenal who had the best chance of the first half when Nacho Monreal picked out Theo Walcott in the penalty area, but with the England man's header seemingly bound for the net Neuer reached back to claw out the effort and keep the scoreline goalless.
Bayern started the second half on top as they looked to continue their 100% record, and after Costa fired over from 25 yards, Lewandowski tested Cech with a fierce drive after the Polish striker was allowed his first clear sight of goal.
Laurent Koscielny slid in to deny Lewandowksi as the hosts pressed for a breakthrough and when Muller flashed an effort narrowly wide from the edge of the box it looked ominous for Arsenal, but the game's big moment arrived seconds later.
Neuer came for a free kick but completely missed Santi Cazorla's floated ball from deep and Giroud, who scored minutes after coming on against Watford at the weekend, headed home just three minutes after replacing Walcott to send the home fans wild.
The Frenchman should have doubled the lead just minutes later, but he could only head straight at Neuer after rising unmarked to meet a corner.
Bayern had just one chance to find an equaliser, when Lewandowski uncharacteristically hesitated in front of goal and allowed Koscielny to clear.
Arsenal went down the other end and put the game beyond doubt in the fourth minute of added time as Hector Bellerin won the ball and squared to Ozil, whose effort was ruled to have crossed the line despite Neuer's best effort.
There was barely time to restart as Arsenal secured a famous victory over the German champions to kickstart their Champions League campaign and move into third in Group F.