Clermont and Toulon will await the winners of next weekend's quarter-finals when the Top 14 play-offs get underway.
Clermont secured first place after thrashing La Rochelle, although any threat to their top spot disappeared with Montpellier's defeat at Racing 92.
However because of that Montpellier loss, Toulon were able to leapfrog them into second place after their bonus-point win over UBB.
Castres rounded out the play-offs by defeating Stade Français at home, but even though Bordeaux-Bègles couldn't snatch sixth place on the final day they have still qualified for next season's Champions Cup after finishing seventh.
This year's final will be played on June 24 at the Nou Camp in Barcelona.
Top 14 2015/2016 Play-offs
Quarter-finals – to be played on June 11/12
Montpellier (3) v Castres (6)
Racing 92 (4) v Toulouse (5)
Semi-finals – to be played on June 19/20 at Roazhon Park, Rennes
Clermont (1) v lowest qualifying side
Toulon (2) v highest qualifying side