Uncapped English fly-half Joe Simmonds slotted 15 points as surprise packages Pau beat Stade Francais 30-6 on Saturday to take the lead in the French Top 14.
Pau, usually involved in the relegation scrap, moved above Toulon with their sixth win from eight games this season.
Former Exeter Chiefs playmaker Simmonds, 26, kept his place as the league's top points-scorer with a fine display for Pau, who will be boosted by the arrival of New Zealand lock Sam Whitelock next week on a two-year deal.
Third-placed Stade Francais' only points of the game came from Joris Segonds' penalty and drop goal.
Elsewhere, controversial former French rugby federation president and ex-France head coach Bernard Laporte lost his first game as Montpellier director of rugby with a 26-21 defeat by promoted Oyonnax.
Montpellier, champions in 2022, are bottom of the table after seven straight defeats.
"We're a team that is doubting itself, a bit confused," Laporte told Canal+.
"Now the objective is simple, we're playing for safety.
"Everyone has to commit, think only of that, when they wake up in the morning, when they shave, when they go to sleep."
Former Ireland fly-half Paddy Jackson scored a try, a conversion, a penalty and a drop goal as Lyon beat Bayonne 42-29 for just their third success of the season.
France winger Damian Penaud became the first player to score four tries in a Top 14 game since 2018 as Bordeaux-Begles hammered Perpignan 46-22.
- Kolisi debut -
Earlier, Fiji winger Setariki Tuicuvu scored twice as Toulon easily overcame Castres 41-19 to temporarily move to the summit of the table.
His fellow winger Gael Drean, who was playing in the fifth tier of French rugby two years ago, also crossed on two occasions for 14-man Toulon after centre Jeremy Sinzelle was sent off early in the second half.
A minute's silence will be held before each game at all levels of the sport in France this weekend after a 16-year-old player named Thomas was killed during a night out last week.
Later on Saturday, winger Lucas Tauzin's double helped Toulouse to a 31-10 bonus-point win over Clermont, lifting them to sixth and the final play-off berth.
On Sunday, South Africa's two-time World Cup winning captain Siya Kolisi will make his Racing 92 debut against Ronan O'Gara's La Rochelle with a win potentially taking the Parisians above Pau to top spot.
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