Clermont booked a place in the Top 14 Final on Saturday but they needed extra time to overcome Toulon 35-29 in their semi-final in Saint-Etienne.
A drama-filled match saw the sides end the regulation 80 minutes level at 22-all.
Twenty minutes of extra time - including a try for each side, a drop goal and a couple of penalties - ensued to see Clermont grab the spoils.
They will now face Perpignan in a rematch of last year's final at the Stade de France on May 29, Clermont's fourth consecutive final. (Of course they have yet to win one.)
Clermont had the upper hand at scrum time in the first half and were the far more ambitious side. Anthony Floch replied to Jonny Wilkinson's early penalty to level the scores after five minutes. But Wilko made sure Toulon led 9-6 at half time thanks to two penalties to Morgan Parra's one.
Toulon offered very little on attack rather basing their game on aggressive defence and the boot of their star fly-half.
As expected, Clermont played their usual expansive game and pushed RCT into enough mistakes to allow Morgan Parra - who was near flawless from the kicking tee - to bring les Juanards level shortly after the break.
Two more penalties from the feisty scrum-half put Clermont 15-9 in front in the 57th minute when Olivier Missoup went off his feet.
But the Toulon scrum made a strong come back in the second half winning a penalty and allowing Wilkinson to narrow the gap to three points going into the final quarter.
Clermont looked to have the match in bag when replacement prop Davit Zirakashvili crashed over with ten minutes left on the clock after Aurélien Rougerie's charge had the RCT defence going backwards.
But the Georgian's try finally spurred Toulon to attack, and attack they did, with Sonny Bill Williams touching down in the 75th minute to end a move started 100m earlier.
Wilkinson's conversion and then his penalty two minutes from the hooter leveled the scores to set up extra time.
Clermont spent the first ten half of extra time camped in the Toulon 22. The ASMCA scrum bounced back in style and the Clermontois led 25-22 at the break thanks to a Brock James penalty (Parra had been replaced soon after Zirakashvili's try).
After the restart, James slotted the drop of the year, from 55m out, to put Clermont six points ahead.
Julien Malzieu then beat Gabiriele Lovobalavu in an 80m sprint to touch down his own kick ahead and give Clermont a comfortable lead.
More drama was to follow however when Toulon replacement scrum-half Fabien Cibray chipped ahead and scored. Wilkinson's conversion reduced the gap to six pints again, but the Varois were unable to pull the game from the fire for second time, handing Clermont a memorable victory.
Tries: Williams, Cibray
Cons: Wilkinson 2
Pens: Wilkinson 4
Tries: Zirakashvili, Malzieu
Cons: Parra, James
Pens: Parra 4, James
Drops: Floch, James
RC Toulon: 15 Luke Rooney, 14 Gabiriele Lovobalavu, 13 Mafileo Kefu, 12 Sonny Bill Williams, 11 Tana Umaga, 10 Jonny Wilkinson, 9 Pierre Mignoni, 8 Juan-Martin Fernadez Lobbe, 7 Joe El Abd, 6 Joe Van Niekerk (cap), 5 Jocelino Suta, 4 Kristian Chesney, 3 Davit Kubriashvili, 2 Sébastien Bruno, 1 Laurent Emmanuelli.
Replacements: 16 Philip Fitzgerald, 17 Saimone Taumeopeau, 18 Fotunuupule Auelua, 19 Ross Skeate, 20 Olivier Missoup, 21 Felipe Contepomi, 22 Fabien Cibray, 23 Tonga Lea'aetoa.
Clermont Auvergne: 15 Anthony Floch, 14 Napolioni Nalaga, 13 Aurélien Rougerie (cap), 12 Joubert, 11Julien Malzieu, 10 Brock James, 9 Morgan Parra, 8 Elvis Vermeulen, 7 Alexandre Lapandry, 6 Julien Bonnaire , 5 Thibault Privat, 4 Jamie Cudmore, 3 Martin Scelzo, 2 Mario Ledesma, 1 Thomas Domingo.
Replacements: 16 Benoît Cabello, 17 Davit Zirakashvili, 18 Julien Pierre, 19 Alexandre Audebert, 20 Kevin Senio, 21 Tasesa Lavea, 22 Gonzalo Canale, 23 Lionel Faure.
Referee: Jérôme Garces