Arsenal missed the chance to move level on points with fourth-placed Tottenham as Southampton won at St Mary’s to inflict a third successive defeat on Mikel Arteta’s team.
Jan Bednarek scored the game’s only goal late in the first half after the Gunners had failed to adequately deal with a Saints corner.
The Ghanaian was benched in the 1-0 victory following his abysmal performance in Southampton’s 6-0 defeat to Chelsea the previous weekend.
Bukayo Saka was denied from point-blank range by Southampton goalkeeper Fraser Forster with the score still goalless, but further clear-cut openings proved hard to come by for the visitors until the closing stages of the second half.
Emile Smith Rowe forced another fine save out of Forster after latching on to Yan Valery’s attempted clearance, before Martin Odegaard dragged a left-footed shot wide of the near post after cutting in from the right.
Forster produced yet another impressive stop to deny Granit Xhaka late on as Arsenal desperately piled forward in search of an equaliser.
The Gunners remain three points behind fourth-placed Tottenham – who were beaten at home by Brighton earlier on Saturday – although they do still have a game in hand on their north London rivals.
Southampton, meanwhile, climb to 12th after claiming their first league win since February.