The Gunners fell behind as Shane Long finished from close range after a mix up between Petr Cech and Shkodran Mustafi. Pierre-Emerick Aubameyang drew them level before Danny Welbeck smashed home from the edge of the box. Charlie Austin made an instant impact from the bench to level for the Saints with less than 20 minutes to play.
Danny Welbeck's made up for a stunning miss by scoring the winner with his next opportunity, before emotions flared as Southampton defender Jack Stephens and Arsenal midfielder Mohamed Elneny were sent off in added time.
Here's how the players rated.
Defensive mistakes almost costly
Petr Cech: 6 -Horrible mix-up with Mustafi for Southampton’s first goal, but dealt with everything else thrown at him in general. Will be disappointed that he was let down by his defenders for Charlie Austin’s equaliser.
Hector Bellerin: 6 - Relatively quite going forward, Bellerin was tested defensively but rarely completely beaten. Always an option right on the touchline and combined well with Reiss Nelson.
Callum Chambers: 7 - Composed on the ball, the Englishman helped keep the ball for his team well on numerous occasions. Occasionally struggled but stood firm.
Shkodran Mustafi: 6 - Had to take control of Cedric’s near post cross for the game’s opening goal. A few other nervous moments helped keep Southampton in the game. Still needs to improve on decision making in deep areas of the pitch, with and without the ball.
Sead Kolasinac: 6 - A quiet afternoon for the Bosnian, who got forward well in the first half and was always an option. Rarely tested defensively.
Mohamed Elneny: 7 - Neat and tidy on the ball as always, Elneny’s performance was soured by the late red card. Before that, he broke up play well and got forward when necessary. The Egyptian continues to show his worth within the current Arsenal squad, although he’ll now be missing in their next Premier League match-day squad.
Granit Xhaka: 7 - Like Elneny, Xhaka was rarely wasteful on the ball and covered the midfield area well. Along with going forward, the Swiss international's defensive contribution was excellent, an area of his game that has greatly improved in 2018.
Welbeck stars with strong all-round performance
Danny Welbeck: 8 - Undoubtablely his best performance of the season, Welbeck initially provided the spark that got his side back into the game. His run and delicate flick allowed Aubameyang to score and he did well to create his own chance that resulted in his first goal. An open goal miss with the score at 2-2 almost proved costly, however his closer range winner spared his blushes.
Alex Iwobi: 7 - This wasn’t a perfect performance, but Iwobi’s strength and carrying of the ball was impressive as he became more and more involved in Arsenal’s interplay on the edge of the Southampton penalty area. He’s been criticised for his final ball, however his assist for Welbeck’s goals showed he can be a provider.
Reiss Nelson: 6 - For his first league start in an Arsenal shirt, the 18-year-old will be please with his performance. Exciting on the ball from the start, Nelson drifted well across the frontline and linked up with Aubameyang, Welbeck and Iwobi nicely. Possibly the first time many Arsenal fans will have seen him play in his favoured position, Nelson showed in patches why he is regarded so highly by his manager.
Pierre-Emerick Aubameyang: 7 - The Gabonese forward continued his excellent form since his move from Borussia Dortmund in January. Another excellent finish made it 6 goals in 7 games, and his ability to drop deep and combine with his teammates showed that he is more than just an goalscorer, although he’s clearly very good at that.
Alexandre Lacazette: 5 - A quiet display from the Frenchman who was given barely any opportunity to make an impact. It is good however to see him back in the squad and hungry to play his part as we near the end of the season.
Jack Wilshere: 5 - Like Lacazette, Wilshere struggled to make an impact, meaning his tussle with Jack Stephens was the highlight of his 26 minute display.
Rob Holding: 6 - Brought on during a period of high Southampton pressure, Holding made an excellent block deep in the Arsenal penalty area and won numerous headers to deny the Saints. His possible partnership with Chambers remains questionable, however only match time next to each other will see it improve.