Southampton were undone by two second-half goals, as Arsenal claimed their first Premier League victory at St Mary’s in 14 years.
Alexis Sanchez popped up with a moment of brilliance for the opening goal whilst Olivier Giroud added a second.
Largely invisible until then, Sanchez’s 20th Premier League goal makes him the first Arsenal player since Robin van Persie to reach that milestone since 2011/12.
Manolo Gabbiadini and Nathan Redmond were each denied first-half goals with the hosts conceding a third consecutive clean sheet to the opposition’s keeper.
Gabbiadini’s point-blank effort was kept out by a sliding Petr Cech with 31 minutes gone whilst Redmond had a well-driven shot from distance palmed away nearing the stroke of half-time.
Arsenal, who had a host of half chances, were without a shot on target in the opening half against a compact Southampton.
But the visitors started the second-half brightly with Aaron Ramsey coming close, only for the chance to be thwarted by his own teammate.
Sanchez, however, pushed Arsenal ahead to the frustration of Southampton on 60 minutes when he left a pair of defenders on the floor before slotting home.
Sofiane Boufal, who had been relegated to the bench, tried to bring one back after twisting and turning at the edge of the box, but he could only find the stands.
Arsenal would double their lead seven minutes from full-time, as substitute Olivier Giroud headed past Forster thanks to Ramsey who flicked the ball back into the six-yard area.
Southampton: Forster, Bertrand, Yoshida, Stephens, Cedric, Davis (c), Romeu, Ward-Prowse (Boufal 70), Redmond (Long 70), Tadic (Rodriguez 80), Gabbiadini.
Unused subs: Hassen (GK), Pied, Caceres, Hojbjerg.
Bookings: Ward-Prowse (44).
Arsenal: Cech (c), Monreal, Mustafi, Holding, Gibbs, Xhaka, Ramsey, Oxlade-Chamberlain (Bellerin 36), Alexis, Ozil (Coquelin 89), Welbeck (Giroud 80).
Unused subs: Ospina (GK), Gabriel, Iwobi, Walcott.
Goals: Alexis Sanchez (60), Giroud (83).
Bookings: Ozil (73), Bellerin (90+3).