Champions Lyon slumped to a shock 2-0 defeat at French first division strugglers Guingamp, while PSG and Lille also suffered on their travels.
Paris Saint-Germain's dreadful run continued, blowing a 1-0 lead to lose 3-2 at Montpellier while league leaders Lille lost 2-1 at plucky Sochaux.
Lille are joined at the top by Nantes, though Monaco, Marseille and Nice have the chance to overtake them in Sunday's matches.
Lyon started with new signing Giovane Elber, whom they stole from under Monaco's noses midweek, but the striker has yet to prove he can fill fellow Brazilian Sonny Anderson's boots.
Two first half goals in the space of six minutes from Burkina Faso forward Moumouni Dagano and Argentine central defender Fabrizio Fuentes finally lifted tiny Breton outfit Guingamp off the foot of the table and left the champions languishing in eighth place.
Former Guingamp forward Florent Malouda, who last month signed a five-year contract with Lyon, failed miserably on his return to Brittany, fluffing a solo break faced with keeper Ronan Le Crom on 29 minutes.
Dagano finally opened the scoring after 33 minutes following a poor clearance from Edmilson.
Six minutes later the home side scored a second with another new recruit Fuentes exploiting another poor clearance.
Lyon desperately tried to make up lost ground after the break but the Guingamp keeper made a string of saves from Malouda and Elber as the home side closed down their defences.
"We're not going to find any excuses for this," Malouda told OL Tele.
"I know Guingamp and we didn't respect our opponents enough. To say Elber's arrival disrupted up is a false excuse."
Paris Saint-Germain coach Vahid Halilhodzic will be under even more pressure after their 3-2 setback at Montpellier.
Although PSG have started scoring, thanks to a brace from Brazilian striker Reinaldo, Halilhodzic has the league's leakiest defence and their third defeat in five leaves them fourth from bottom.
Reinaldo's double was matched by Montpellier's Habib Bamogo, and Portuguese forward Rui Pataca won it six minutes from time after Reinaldo had seemingly rescued a point for the underachievers 11 minutes earlier.
Leaders Lille took a 6th-minute lead at Sochaux through Philippe Brunel, but Brazilian Francileudo Santos equalised three minutes later and before defender Eric Abidal, on loan from Monaco, shot through his own goal to end Lille's unbeaten start.
Nantes' goalless draw with Bordeaux was enough to send them joint-top with Lille. The 2001 champions are proving they can play without Eric Djemba-Djemba, sold to Manchester United.
UEFA Cup side Auxerre inflicted a first defeat on Rennes, French international Djibril Cisse scoring the opener in a 2-1 win.
Last season's second division champions Toulouse are still without a win after former France striker Florian Maurice set visitors Bastia on the road to a 2-0 triumph.
Fellow newcomers Le Mans are similarly winless after Strasbourg raced to a 3-0 away victory.
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