Tottenham Hotspur's hopes of a top-four finish suffered a setback as Leandro Trossard's last-minute goal earned Brighton & Hove Albion back-to-back wins over north London clubs.
Spurs struggled to break down the visitors throughout the contest, although they improved in the second half, with Son Heung-min's goalbound shot was blocked by Joel Veltman.
Graham Potter's side, who had beaten Arsenal last time out, themselves threatened when Hugo Lloris was called upon to deny Tariq Lamptey's effort and a Lewis Dunk header.
The breakthrough arrived in the final minute of regulation time, Trossard pouncing on hesitant defending to turn Eric Dier and poke in from close range.
Substitute Steven Bergwijn passed up a good chance to equalise in added time but Brighton held on for victory.
A first defeat in five keeps fourth-placed Spurs on 57 points, three ahead of Manchester United and Arsenal, the Gunners having played one match fewer.
Brighton are up to 10th place with 40 points.
Spurs: 23 Apr v Brentford (A)
Brighton: 20 Apr v Man City (A)
Referee: Craig Pawson. Assistants: Ian Hussin, Dan Robathan. Fourth official: Tony Harrington. VAR: Lee Mason. Assistant VAR: Constantine Hatzidakis.