Bordeaux-Begles scored two tries in the last eight minutes to earn a 37-19 win over Lyon that moved them above their opponents at the Top 14 summit.
Lyon came into Saturday's match at Stade Chaban-Delmas with a two-point lead at the top of the table but they now trail by three after Bordeaux landed a bonus-point triumph.
The match was hanging in the balance with the hosts 20-19 ahead going into the closing stages, but Seta Tamanivalu and Santiago Cordero scored pivotal converted tries in quick succession.
Elsewhere, La Rochelle failed to keep hold of third place as they fell to a last-gasp 21-20 loss away to struggling Stade Francais.
Facundo Bosch appeared to have given the visitors a come-from-behind victory, but Stade Francais' Nicolas Sanchez crossed in the fourth minute of stoppage time after Jules Plisson had been sent to the sin bin.
La Rochelle drop below Toulon, whose wing Daniel Ikpefan dotted down twice in a comfortable 34-17 home win over Brive.
Clermont Auvergne are sixth after they stormed back with 10 points in the final seven minutes to grab a 23-20 win at Pau.
In another close encounter, Montpellier held off a late Bayonne fightback to record a 31-29 home victory, with Nemani Nadolo scoring a hat-trick.