Swansea City came from behind to beat Arsenal at the Emirates Stadium and move six points clear of the relegation zone.
The hosts started much the brighter and after several near misses, they took the lead when Joel Campbell thundered his effort home from an angle.
But Swansea hit back before the break as Wayne Routledge beat Petr Cech with a cool finish after being played through by Jack Cork, and they completed the dramatic turnaround with 15 minutes left as Ashley Williams turned home a Gylfi Sigurdsson cross to send the 2,000 travelling fans into raptures.
Arsenal tried to respond late on but the Swans defence held firm to hold on for a crucial three points ahead of a set of important fixtures in the coming weeks.
Victory moved the Swans onto 30 points - six clear of third-bottom Norwich City.
Swansea City made six changes to the side that lost to Tottenham three days previously in the Premier League.
In defence, Angel Rangel and Federico Fernandez made way for Kyle Naughton and Jordi Amat, while youngster Stephen Kingsley was handed his first Premier League start in place of Neil Taylor.
Leroy Fer made his first start for the club in midfield in place of Leon Britton, with Wayne Routledge returning to the starting line-up as Gylfi Sigurdsson moved to the substitutes bench.
Meanwhile, Alberto Paloschi - who scored his first Swansea goal in Sunday’s defeat at White Hart Lane - was replaced by Bafe Gomis in attack.
With head coach Francesco Guidolin missing the game due to a chest infection, Alan Curtis took the reigns at the Emirates Stadium.
ARSENAL: Petr Cech, Per Mertesacker (capt), Gabriel, Mesut Ozil, Olivier Giroud, Aaron Ramsey, Alexis Sanchez (Theo Walcott, 74), Nacho Monreal, Hector Bellerin, Joel Campbell (Danny Welbeck, 66), Francis Coquelin.
SUBS: David Ospina, Kieran Gibbs, Mathieu Flamini, Calum Chambers, Mohamed Elneny.
SWANS: Lukasz Fabianski, Kyle Naughton, Jordi Amat, Ashley Williams (capt), Stephen Kingsley, Jack Cork, Leroy Fer (Jay Fulton, 71), Ki Sung-Yueng (Gylfi Sigurdsson, ht), Wayne Routledge, Andre Ayew (Angel Rangel, 88), Bafetimbi Gomis.
SUBS: Kristoffer Nordfeldt, Federico Fernandez, Modou Barrow, Alberto Paloschi.
The Emirates Stadium has been a happy hunting ground for Swansea since they won promotion, with just one defeat in four trips to North London in the Premier League.
But it was a tough opening quarter for the visitors on this occasion as Arsenal created three decent openings within the first ten minutes.
First it was Olivier Giroud who had a sight of goal before he saw a low shot blocked by Ashley Williams, and the Swans skipper was called into action soon after as he blocked from the same player after a cut back from Hector Bellerin on the right.
But the Gunners’ best chance fell to Alexis Sanchez in the 10th minute as Joel Campbell’s chipped pass was flicked on by Mesut Ozil and after Sanchez jinked past his marker he was unfortunate to see a curling shot come back off the foot of the post.
However, Sanchez played a key role just five minutes later as the home side were rewarded for their dominance by breaking the deadlock.
After patient build-up outside the penalty area, Sanchez picked up the ball on the left edge of the box and he clipped a fine pass into the box for Campbell who produced a lovely left-foot finish on the turn that gave Lukasz Fabianski no chance in the Swansea goal.
The former Arsenal stopper also saved well from Bellerin’s 25-yard drive, while the visitors’ best chance of the opening half an hour came from Leroy Fer as the on-loan midfielder saw a 20-yard effort just evade the crossbar.
That marked a good period of play for Swansea who were seeing more of the ball, and the visitors stunned the Emirates crowd with an equaliser on 33 minutes as Jack Cork played a fine pass through for Wayne Routledge who coolly slotted past Petr Cech for his first away goal since January 2012.
That setback sparked Arsenal back into life and the hosts finished the half strongly as Giroud saw a fierce right-foot volley cannon back off the crossbar on the stroke of half-time.
Half-time: Arsenal 1 Swans 1
The Swans made a change at the break as Gylfi Sigurdsson was introduced in place of Ki Sung-Yueng.
And it was the visitors who created a couple of openings, with Stephen Kingsley sending in a fine low cross that evaded everyone in the six-yard box, while Andre Ayew drifted in from the right flank before shooting wide of goal.
At the other end, Alexis Sanchez shot wide of the left-hand post as the Gunners looked to wrestle back the initiative.
The hosts then made their first change of the evening as goal scorer Joel Campbell was replaced by Danny Welbeck with a quarter of the game remaining, while youngster Jay Fulton was introduced in place of Leroy Fer for Swansea.
But it was Arsenal who came mightily close to retaking the lead as Sanchez saw a 20-yard free-kick come back off the upright with Lukasz Fabianski beaten.
However, the contest took a dramatic twist with 15 minutes left to play as the Swans took the lead.
After Andre Ayew was fouled on the right flank, Gylfi Sigurdsson whipped in a fantastic free-kick that was turned home by captain Ashley Williams from six yards out.
Olivier Giroud saw a header comfortably saved by Fabianski as Arsenal looked to get back on level terms, but the Swansea defence held firm throughout the closing stages.
And the visitors worked tirelessly for the final moments as the whistle went to cap a memorable night in North London.