The boot of Benjamin Urdapilleta made the difference as Castres Olympique beat Montpellier 29-13 to claim a surprise Top 14 title on Saturday.
Urdapilleta slotted home five penalties and converted tries by Julien Dumora and Steve Mafi to give Castres their first title since 2013.
Montpellier, who finished the regular season in top spot, replied through penalties by Ruan Pienaar and Francois Steyn and a try by Jesse Mogg.
Castres, who finished the season in sixth place, had to go through a playoff tie on their way to the final. (Reporting by Julien Pretot; Editing by Clare Fallon)