Gazelec Ajaccio picked up their first Ligue 1 win at the 11th time of asking, ending Nice's four-match winning run with a 3-1 triumph in Corsica.
Hatem Ben Arfa had inspired Nice's surge in form, taking them up to sixth in the table, but they looked bereft of ideas against Gazelec.
Gregory Pujol got the minnows off to a dream start, scoring inside the first minute.
Though Gazelec captain Roderic Filippi could only turn Ricardo Pereira's cross into his own net 10 minutes later, he made amends in the best possible way just after the half-hour, restoring the hosts' lead with a towering header from Damjan Djokovic's corner.
Djokovic himself gave Gazelec a two-goal cushion shortly before the interval, and it proved enough to make history as Nice failed to muster a response after the break - GFC substitute Jerome Le Moigne's late red card doing little to dampen the party atmosphere as Thierry Laurey's men clambered off the foot of the table.
Paris Saint-Germain will have the chance to open up a seven-point lead at the top after second-placed Angers drew 0-0 at home to Guingamp.
Breton rivals Lorient and Rennes played out a 1-1 draw, while Montpellier registered their second win of the Ligue 1 season courtesy of a 2-0 success against Bastia.
