Arsenal's dismal run of form rolled on as Neal Maupay's superb header earned Brighton and Hove Albion a 2-1 victory at Emirates Stadium.
Alexandre Lacazette's 50th-minute equaliser on his 100th appearance for the club looked set to pave the way for Arsenal to claim its first win under caretaker boss Fredrik Ljungberg.
Yet Brighton, which had deservedly taken the lead through Adam Webster in the first half, managed to wrest back control after David Luiz had a goal ruled out by VAR.
And it was Maupay who had the final say, as he brilliantly turned home Aaron Mooy's cross in the 80th minute to end Brighton's three-match losing streak and condemn Arsenal to its longest winless streak since 1977.
Having started brightly, Arsenal swiftly grew frustrated as Brighton began to click into gear, with Maupay and Davy Propper testing Bernd Leno in quick succession.
Brighton deservedly had the lead nine minutes before half-time, Webster thumping home after Arsenal failed to clear its lines from a corner.
Joe Willock looked set to pull Arsenal level four minutes later, but Mat Ryan pulled off a superb stop from the youngster's header.
But Arsenal was level five minutes into the second half as Lacazette's looping header from Mesut Ozil's cross looped into the top-left corner.
Hector Bellerin was inches away from teeing up Pierre-Emerick Aubameyang soon after, though Leno had to be alert to deny Maupay at the other end.
David Luiz thought he had put Arsenal ahead just after the hour, only for VAR to correctly disallow the goal for offside.
Brighton made its good fortune count – Maupay sending a brilliant glancing header across Leno as the Seagulls clinched their maiden away win over Arsenal.
- What does it mean? No Emery, still the same problems -
Arsenal is now without a win in nine matches in all competitions, and with the Gunners sitting 10th, 10 points below the top four, its season seems to be quickly spiralling out of control.
Sacking Unai Emery does not seem to have had the desired effect, and if the boos ringing around the Emirates at full time are anything to go by, the club must move to appoint a proven coach as quickly as possible.
- Maupay makes history for Brighton -
Graham Potter's side was unfortunate not to claim something from its trip to Anfield on Saturday, but this time it took its chances, with Maupay's clinical finish ensuring a famous victory.
- Aubameyang fails to step up -
Much was made of Granit Xhaka losing the Arsenal captaincy, but his replacement in the role – Pierre-Emerick Aubameyang – was largely anonymous throughout on Thursday, and the one chance he had, when he was played through one-on-one midway through the second half, he snatched at.
- What's next? -
A London derby is next up for Arsenal, which faces West Ham United on Monday. Brighton, meanwhile, hosts Wolves on Sunday.