By Chris Harris at London Stadium
We produced a stunning second-half comeback to end our long winless run in the Premier League.
Gabriel Martinelli, Nicolas Pepe and Pierre-Emerick Aubameyang scored in the space of eight minutes - with Pepe's stunning effort the pick of the bunch.
The first half was flat to say the least, but West Ham found a goal when we failed to clear and Pablo Fornals' cross was headed in by Angelo Ogbonna - with a sizeable deflection off Ainsley Maitland-Niles.
We'd been underwhelming up to that point and struggled to get going after the break too, but our confidence started to return when Martinelli fired home confidently from a Sead Kolasinac pass.
The game was wide open by now and Pepe curled a shot into the top corner to spark a long, loud celebration in the away end.
An elusive three points were within our grasp and they were secured when a flowing move involving Mesut Ozil, Aubameyang and Pepe ended with the latter clipping in a cross for Aubameyang to volley home.
HOW IT HAPPENED
THREE THINGS WE NOTICED
WHAT IT MEANS
Freddie Ljungberg rang the changes after our defeat to Brighton, giving Martinelli his first Premier League start.
The young Brazilian was part of an exciting front four that also included Pepe, Aubameyang and Ozil.
There were changes at the back two with Kieran Tierney, Calum Chambers and Hector Bellerin drafted in.
But the latter had to drop out after picking up a knock in the warm-up. In came Maitland-Niles.
We conclude our Europa League group fixtures with a trip to Standard Liege on Thursday.
Then it's back to the Premier League, with Manchester City visiting the Emirates on Sunday.
Copyright 2021 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source.