An excellent away performance, featuring goals from Nicolas Pepe, Bukayo Saka and Alexandre Lacazette, saw Arsenal come from behind to record their fifth win in six games.
The result sees the Gunners move above Southampton, who won their previous meeting in the FA Cup at the weekend, with the two clubs sitting eighth and 11th respectively.
Arsenal started quickly, Lacazette missing a one-on-one in the opening seconds of the game; two minutes later, Stuart Armstrong’s half-volley put Southampton ahead.
But Arsenal came back at them, equalised on eight minutes through Pepe, and though the home side took control of the game around the half-hour mark, it was the visitors who scored again, Saka’s fourth goal in six games taken with characteristic expertise.
Southampton did their best in the second half, but they lacked the wit and zip to penetrate Arsenal’s low block, and a clinching goal on the counter always looked more likely than an equaliser, duly arriving on 73 minutes when Cedric Soares and Saka combined to give Lacazette a tap-in. Arsenal are coming.