Castres claimed their first French title since 1993 with a shock 19-14 victory over European champions Toulon in Saturday's Top 14 Final in Paris.
South African scrum-half Rory Kockott - who finished the season as the tournament's top points scorer - broke clear for the only try of the game on the stroke of half time to give Castres a 10-3 lead at the interval.
Veteran fly-half Jonny Wilkinson kicked Toulon back into contention to leave the scores at 10-9 going into the final ten minutes but two late drop goals from pivot Remi Talès and a penalty from Kockott secured victory for Castres in their first ever match at the Stade de France.
Delon Armitage scored a try for Toulon after the final hooter, but his score proved too little too late for the star-studded side whose performance was plagued by uncharacteristic handling errors.
For Castres it was a fourth French title, the perfect send-off for Racing Metro-bound coaching pair Laurent Labit and Laurent Travers.
Few pundits gave les Tarnais much chance of upsetting Toulon, who were aiming to become the first club to do the French-European double since Toulouse in 1996. But, like they did a week ago with their surprise win over Clermont, Castres measured their effort to perfection, playing to their strengths by building on their impressive scrum and striking when the iron was hot.
It looked set to be a bruising dogfight similar to last year's try-less final until a moment of genius from Kockott on the stroke of half-time.
With fly-half Talès in the pockett getting ready for a drop goal attempt that would have sent the underdogs into the dressing-rooms in front, the South African showed a slight of hand that a magician would have been proud of.
He dummied the pass back to his number 10, diverting the attention of Toulon's chargers, before darting through a gaping hole, with Frederic Michalak totally flummoxed, to dot down under the posts.
Kockott's own conversion took the score out to 10-3 at the break with Toulon manager Bernard Laporte, who was already halfway down the tunnel, looking on furiously.
Before that inspirational score, which came after the half-time buzzer, it had been a midfield stalemate.
Wilkinson had hit the post with the first penalty attempt of the night before being given a second opportunity straight in front of the woodwork moments later.
Seremaia Bai almost got Castres going with a weaving break but the underdogs spilled the ball in the corner five yards out.
Yet the European champions committed suicide as Matt Giteau spilled the ball almost on his line and from the resulting scrum, Toulon were penalised and Kockott levelled the scores on 14 minutes.
Castres were pinged for not rolling away but Wilkinson missed for the second time in three attempts when his penalty from halfway dropped just under bar.
Toulon must have had some hairdryer treatment from Laporte because they were a different animal after the break.
Bastareaud charged to within inches of the line before Castres were penalised and Wilkinson knocked over his second penalty.
The game had really opened up as Ibrahim Diarra wasted an overlap 10 yards out by trying to go it alone. Castres were subsequently awarded a penalty but Kockott hit the upright.
Toulon almost caved in again, trying to run the ball out from behind their line and after Chris Masoe dropped it, replacement scrum-half Sebastien Tillous-Borde saved the day by getting his hands under the ball to prevent Talès from touching down.
Wilkinson missed his third kick of the night when hitting the post from halfway but he then slotted over a penalty from the 10-yard line as Toulon closed to within a point at 10-9 with 13 minutes left.
Yet Castres brilliantly manipulated themselves into a drop-goal position twice in the space of two minutes and Tales knocked both over to leave Toulon needing a converted try to draw level.
That sparked a crazy finale as more handling errors denied Toulon the chance to hit back before Kockott sealed victory with a penalty, only for Armitage to go over in the left corner for an unconverted consolation try after the final buzzer.
Try: D. Armitage
Pens: Wilkinson 3
Drops: Talès 2
Rugby Club Toulonnais: 15 Delon Armitage, 14 Rudi Wulf, 13 Mathieu Bastareaud, 12 Matt Giteau, 11 Alexis Palisson, 10 Jonny Wilkinson (c), 9 Frederic Michalak, 8 Chris Masoe, 7 Juan Fernandez Lobbe, 6 Danie Rossouw, 5 Nick Kennedy, 4 Bakkies Botha, 3 Carl Hayman , 2 Sebastien Bruno, 1 Andrew Sheridan.
Replacements: 16 Jean-Charles Orioli, 17 Xavier Chiocci, 18 Jocelino Suta 19 Joe van niekerk, 20 Steffon Armitage, 21 Maxime Mermoz, 22 Sébastien Tillous-Borde , 23 Davit Kubriashvili.
Castres Olympique: 15 Brice Dulin, 14 Romain Martial, 13 Romain Cabannes, 12 Seremaia Baï, 11 Marc Andreu, 10 Remi Talès, 9 Rory Kockott, 8 Antonie Claassen, 7 Yannick Caballero, 6 Ibrahim Diarra, 5 Rodrigo Capo Ortega, 4 Christophe Samson, 3 Karena Wihongi, 2 Brice Mach, 1 Saimone Taumoepeau.
Replacements: 16 Mathieu Bonello, 17 Yannick Forestier, 18 Joe Tekori, 19 Janie Bornman, 20 Romain Teulet, 21 Daniel Kirkpatrick, 22 Paul Bonnefond, 23 Mihaïta Lazar.
Venue: Stade de France, St. Denis (Paris)
Referee: Jérôme Garcès
Assistant referees: Pascal Gauzère, Sébastien Clout