Bukayo Saka starred as Arsenal avenged their FA Cup exit against Southampton with a 3-1 win in the Premier League rematch on Tuesday.
Mikel Arteta's side saw their reign as FA Cup holders ended in a lacklustre 1-0 fourth-round defeat at St Mary's on Saturday.
But the Gunners made amends for that with a convincing success on their return to Southampton four days later.
Unfazed by Stuart Armstrong's early strike for the hosts, Arsenal were ahead by half-time thanks to goals from Nicolas Pepe and Saka.
Alexandre Lacazette netted in the second half as Arsenal came from behind to win an away league game for the first time since Arteta took charge in December 2019.
Arsenal are up to eighth place after a fifth victory in their past six league matches, putting them in a rich vein of form before Saturday's visit from title contenders Manchester United.
Southampton, stuck in mid-table, have won only one of their last seven league games.
Arsenal captain Pierre-Emerick Aubameyang was unavailable again for "personal family reasons" after also missing last weekend's FA Cup loss.
Saka, Lacazette and Emile Smith Rowe were recalled as Arteta made five changes and the reshuffled Gunners should have been ahead inside the first minute.
Granit Xhaka's defence-splitting pass picked out Lacazette's run, but the French striker shot straight at Alex McCarthy with only the Saints keeper to beat.
Southampton made the most of that escape to take the lead in the third minute.
With four successive league clean sheets before their trip to St Mary's, Arsenal had been looking unusually solid at the back, but Armstrong's goal would have infuriated Arteta.
James Ward-Prowse curled his corner to the edge of the area, where Armstrong, left unmarked by the dozing Pepe, smashed a fierce strike past Arsenal keeper Bernd Leno.
If Pepe was the scapegoat for Southampton's opener, then the Ivory Coast winger made amends in the eighth minute.
After Thomas Partey pressed Southampton into conceding possession, Xhaka's pass sent Pepe racing clear and he slotted into the far corner for his sixth goal of the season.
Cedric Soares was inches away from putting Arsenal ahead against his old club with a volley that curled just wide from the edge of the area.
Leno sprawled to his right to keep out Che Adams's header from Jake Vokins's cross.
Saka has underlined his billing as one of Arsenal's brightest young stars this season and the 19-year-old struck in clinical fashion in the 39th minute.
Lacazette's pass gave Saka a chance to run behind the Southampton defence and when McCarthy rashly sprinted off his line, the Arsenal winger darted round him and rolled a composed finish into the empty net.
Saka's fourth goal in his last six league appearances should have been cancelled out by Theo Walcott soon after the interval, but the former Arsenal winger shot straight at Leno.
It was a crucial miss as Arsenal held firm and wrapped up the points in the 73rd minute.
Cedric's superb long pass found Saka in the Southampton area and he sent a low ball across the six-metre box for Lacazette to bundle home.
