Lewis Dunk put Brighton ahead when he hooked the ball home from a corner after it dropped to him inside the six-yard box.
The Seagulls added a second when Laurent Koscielny’s misplaced pass was intercepted and Pascal Gross teased a high cross into the box for Glenn Murray to head past Petr Cech.
Arsenal pulled a goal back when Brighton failed to clear their lines. Granit Xhaka fed the ball into Pierre Emerick-Aubameyang, who cleverly flicked the ball home with the outside of his boot.
Arsenal dominated possession in the second half and had a late chance to equalise through Aubameyang but he could only shoot straight at Mathew Ryan.
The Gunners were also fortunate not to have Sead Kolasinac, who had already been booked, sent off for a challenge that ended Ezequiel Schelotto’s involvement.
Arsenal were meek in back-to-back 3-0 defeats to Manchester City in the Carabao Cup final at Wembley last Sunday and at the Emirates in the Premier League our days later.
Losing to Pep Guardiola’s irresistible champions-elect is one thing, but to a Brighton side battling relegation will not be so palatable for Arsenal fans growing increasingly tired of Wenger’s reign.
It was the first time the Gunners had lost four consecutive matches since October 2002 in a run that saw them beaten by Everton, Auxerre, Blackburn and Borussia Dortmund.
They were defending champions that season and ended the campaign as runners-up to Manchester United but retained the FA Cup.
Over 15 years later and things are not quite so rosy for Wenger with the club seemingly in terminal decline.
Wenger, initially at least, did not look like a man under pressure at the Amex as he warmly embraced Brighton counterpart Chris Hughton and shared a joke with a photographer.
However, by early in the second half with his side 2-1 down his mood darkened and he nervously pulled apart a coffee stirrer as he sat on the bench.
The travelling fans, who held up ‘Wenger out’ banners at the final whistle, will want the Arsenal board to wake up and smell it.
