Charlie Austin’s 85th-minute header clinched 3-2 victory for Southampton Manager, Ralph Hasenhuttl, on his home debut and ended Arsenal’s 22-match unbeaten run.
In a see-sawing encounter, the hosts took the lead after 20 minutes as Danny Ings muscled home a header from Matt Targett’s cross.
Henrikh Mkhitaryan nodded in shortly after for Arsenal, following good work by Alex Iwobi and Nacho Monreal – but Ings struck again just before the break.
Nathan Redmond’s floated cross was precise and Ings cushioned a looping effort into the far corner.
Arsenal turned the screw in the second half and restored parity as Mkhitaryan’s shot deflected in off Jannik Vestergaard.
The Gunners had their chances with Alex McCarthy impressing in the home goal, but Southampton were dangerous on the break and Shane Long had a goal rightly ruled offside before providing a teasing cross for Austin’s winner.
The victory takes Southampton out of the relegation zone and up to 17th.
At the final whistle, Austrian Hasenhuttl – nicknamed the ‘Klopp of the Alps’ during his spell at previous club RB Leipzig – celebrated on the pitch with his players before whipping up more decibels from the home support.
With rivals Chelsea winning away at Brighton, Arsenal are now three points adrift of the top four.
Earlier in the week, Hasenhuttl had sent free drinks vouchers to Southampton’s season ticket-holders to mark his first game at St Mary’s. His accompanying letter promised an “intensive and very hard-working” environment and his players responded by trumping Arsenal’s quality with industry and tenacity.
Ings, whose last headed Premier League goal was for Liverpool in Brendan Rodgers’ final match in charge back in October 2015, looked a potent aerial threat, finding space in between Arsenal’s three-man defence to score his two goals.
Also heartening for a team at the wrong end of the table, the Saints defence was galvanised.
Jan Bednarek typified their whole-hearted commitment, sliding in to steal the ball as Pierre Emerick Aubameyang was poised to put Arsenal ahead in the first half.
Hasenhuttl lived every moment on the touchline, visibly reminding himself to stay off the pitch as he celebrated Ings’ first, before ultimately giving way to his emotion and sprinting on to join his players at the final whistle.