To beat Manchester United 3-1 in the Premier League on Monday.
The Gunners trailed 1-0 at halftime after a Bruno Fernandes penalty
But they came out firing in the second half and equalized through Bukayo Saka in the 59th minute.
Arsenal then took the lead through a Declan Rice goal in the 96th minute, and Gabriel Jesus added a third in stoppage time to seal the victory.
The win was a huge boost for Arsenal, who had lost their previous two games.
It also moved them up to fifth place in the table, just two points behind fourth-placed Tottenham Hotspur.
Manchester United, meanwhile, are in a bit of a crisis. They have now lost three of their last four games, and they are in danger of missing out on European football next season.