Clermont beaten by Bordeaux-Begles
Clermont Auvergne won the Top 14 last season, but started the new campaign with a 32-25 loss at the hands of Bordeaux-Begles.
Reigning Top 14 champion Clermont Auvergne began the 2017-2018 season with a loss courtesy of an impressive second-half performance by Bordeaux-Begles at Stade Chaban-Delmas.
Clermont led by seven points at the interval on Sunday (AEST), but was beaten 32-25 as Bordeaux, playing its first competitive game under Jacques Brunel, came on strong in the second half.
Both sides scored three tries apiece, with Simon Hickey's five penalties proving decisive for Bordeaux.
Racing 92 came roaring back from 18-3 down to record a 25-21 victory over Castres, Louis Dupichot claiming the match-winning try with just three minutes remaining.
Arthur Retiere scored two tries as La Rochelle, which finished the 2016-2017 regular season top of the table, won 19-10 at Brive in a match featuring two yellow cards for each side, while Lyon won 25-16 at Stade Francais.
On its return to the top flight, Agen suffered a chastening 48-19 defeat against Montpellier, which had seven different try scorers.
However, fellow newly promoted club Oyonnax was able to hold Toulouse to a 23-23 draw.
Toulon, the beaten finalist last term, faces Pau on Monday (AEST) in the opening round's sole remaining fixture.