Bordeaux Begles' hopes of securing a Champions Cup place and a spot in the Top 14 play-offs evaporated in dramatic fashion as they threw away a 29-point lead to lose 43-36 to Toulouse, who are now certain to finish first in the regular season.
George Tilsley scored a hat-trick as the hosts dominated the opening 40 at Stade Chaban-Delmas, outscoring their opponents five tries to one.
However, Toulouse came roaring back in the second half, with Guillaume Marchand's try kicking off a comeback that saw Arthur Bonneval and Thomas Ramos both go over twice. Ramos also landed four conversions and a penalty to finish with 21 points.
Bordeaux can no longer make the top six, while Toulouse cannot be caught at the summit.
In-form Montpellier sneaked up to sixth, above La Rochelle on points difference, with a 42-25 triumph over Stade Francais that eliminated the latter from play-off contention.
The game was fascinatingly poised at 21-20 with 10 minutes remaining when Stade's Laurent Sempere became the third player to be yellow carded.
Montpellier took full advantage, running in three tries to secure victory and a valuable bonus point.
Sunday's other game saw second-placed Clermont Auvergne beaten 32-11 by Toulon in an ill-tempered fixture. Toulon's Romain Taofifenua was red-carded in the 54th minute, while there were also an astonishing five yellows shown in the second half, four of them significantly hampering Clermont, who were briefly reduced to 12 men.