Lyon surrendered first place in Top 14 as they lost away to Bordeaux-Begles, who won a contest that was closer than the scoreline suggests.
Bordeaux-Begles scored two tries in the last eight minutes to earn a 37-19 win over Top 14 rivals Lyon that moved them above their opponents at the league 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.
Earlier in the contest, Fiji star Semi Radradra had emphatically bounced back from a spell in the sin-bin by scoring a double for Bordeaux as they recovered from an early deficit, Lyon having crossed for the first try of the match.
But while two penalties apiece from Charlie Ngatai and Jonathan Wisniewski kept the visitors within striking distance in a match that was 10-10 at the interval, Mickael Ivaldi's 17th-minute effort proved their only try.
It was a welcome return to form for Christophe Urios' Bordeaux side after their loss to defending champions Toulouse last time out.
Watch: Semi Radradra's double
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 additional 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, Nemani Nadolo scoring a hat-trick.