Petr Cech’s calamitous error helped Swansea to a shock 3-1 victory over Arsenal at the Liberty Stadium.
Nacho Monreal (33) continued his excellent goalscoring form, giving the Gunners the lead but Swansea, who beat Liverpool in their last league outing, hit back straight away through Sam Clucas (34) to go in level at the break.
The hosts were given a helping hand on their way to all three points when Cech hit an attempted clearance straight to Ayew, and the 26-year-old had the easiest of finishes to give his side a much-deserved lead.
Wenger sent on Henrikh Mkhitaryan for his debut and used Olivier Giroud from the bench, despite speculation surrounding his future, but it was Clucas who put the finishing touch on Swansea’s superb night, sweeping home from close range after poor defending to send the hosts out of the relegation zone for the first time in three months
In tricky conditions, Swansea made the brighter start and Alfie Mawson looked set to open the scoring in the eighth minute after meeting Nathan Dyer’s cross at the far post, but Aaron Ramsey’s last-gasp block got Arsenal out of jail.
The Gunners needed another perfectly timed sliding tackle, this time from Mohamed Elneny, to deny Clucas, who was bearing down on goal after being played in by Leroy Fer. There were shouts for a penalty from the hosts but referee Lee Mason rightly waved away the appeals with Elneny getting a clear touch on the ball.
Arsenal struggled to get going as an attacking force but they were in front in the 33rd minute when Mesut Ozil picked out the run of Monreal at the far post, and the full-back poked the ball past Lukasz Fabianski and into the back of the net to net his fourth Premier League goal of the season.
Swansea were unlucky to be behind but they struck back immediately as Mawson’s through ball picked out the run of Clucas, and the midfielder swept the ball past the onrushing Cech.
Arsenal were more assured at the start of the second half but all their improvement was undone when Cech’s awful clearance went straight to Ayew, who made no mistake from close range to roll home his fifth goal in nine games.
Giroud, who could be set for a move away from the Emirates on Deadline Day, and new signing Henrikh Mkhitaryan were sent on in a bid to rescue the Gunners, but Swansea should have extended their lead when Shkodran Mustafi’s poor header picked out Dyer and the forward’s shot struck the outside of the post from 14 yards.
Swansea did get a third as Ayew burst past Mustafi and the excellent Clucas reacted first to beat Cech at the near post to complete a brilliant night for the hosts.