Against a star-studded Toulon side that contained Jonny Wilkinson, Matt Giteau and Steffon Armitage and others, the south-west side managed to clinch their first win in fourth months as they moved out of the relegation zone in the process.
Ole Avei, Louis-Benoit Madaule, Matthew Clarkin, Lachlan Munro and Jefferson Poirot scored the tries as the shock of the day was sealed.
Defending champions Toulouse also suffered an upset as they lost 22-9 to Agen.
Scrum-half Alexis Bales and Gert Muller recorded the tries for Agen, while fly-half Conrad Barnard made no mistake with three penalties.
Bayonne beat Perpignan 13-10, while Grenoble brushed aside Mont de Marsan with a 32-14 result.
Meanwhile, Castres kept up their push for the top spots as they grabbed five tries to beat Stade Francais 44-13, and Montpellier beat Biarritz 33-10 to record a fine win in front of their home fans.