Chilean forward Alexis Sanchez rescued Arsenal from a draw as he scored just two minutes from time to help his club deny Southampton the chance to hold them out for a draw at The Emirates.
Visiting goalkeeper Fraser Forster had kept Arsenal at bay with a collection of fine saves from Danny Welbeck and substitute Olivier Giroud, but he was powerless to prevent their talisman Sanchez pouncing on Aaron Ramsey's cross to score his 14th goal of the season.
Arsene Wenger's side deserved the win after applying intense late pressure but Southampton were forced to play out the crucial final minutes without defender Toby Alderweireld, who suffered a hamstring injury after manager Ronald Koeman had used his three substitutes, The BBC reported.
The victory, coming on the heels of the win at West Bromwich Albion on Saturday, pushed Arsenal into the top six, while Southampton stays third despite a second successive defeat following their home loss against Premier League champions Manchester City on Sunday.
Neither goalkeeper saw serious action until first-half stoppage time, when Southampton's Forster reacted well to turn Welbeck's flicked header over the top. The striker also tried a backheel at the near post but was crowded out by the visitors' defenders.
As anxiety grew inside The Emirates, Wenger made the change demanded by Arsenal's fans when he introduced Giroud, although the decision to take off Alex Oxlade-Chamberlain was met with some jeers.
Giroud almost immediately tested Forster with a snap shot as Arsenal attempted to finally apply concerted pressure on a resolute and well-organised Southampton defence.
It seemed the England goalkeeper was going to keep Arsenal at bay when he showed great athleticism to claw away Giroud's header but, just when it looked like Southampton would survive despite their numerical disadvantage, Sanchez made the breakthrough.
Southampton manager Ronald Koeman said that his side had a good positive reaction after last Sunday, a good first half, good ball possession, a good chance off Pelle.
He claimed that it got more difficult after an hour, adding that Arsenal were pressing more but the difference was 11 versus 10.
Koeman said that his side was unlucky to get a player injured after making all of their substitutions, one knows Arsenal would create chances and in the last few minutes the hosts made it 1-0.
