Leinster are still on track to defend their Heineken Cup title after beating Clermont 19-15 in Sunday's semi-final in Bordeaux.
Leinster will now face Ulster in an all-Irish final at Twickenham on Saturday, 19 May - the team from Dublin's third final in four years.
The match was billed as the 'game of the season' in Europe and the capacity crowd at the 34 500-seater Stade Chaban-Delmas were certainly treated to a tussle of the highest quality.
Clermont led 12-6 at the interval of a cut-and-thrust encounter but Leinster ruled in the second period and took control thanks to a try set up by Rob Kearney and scored by Cian Healy.
The French side looked to have snatched victory in the dying moments however but Wesley Fofana lost control of the ball in the act of crossing the try-line.
The game ended with les Jaunards camped under the posts but referee Wayne Barnes handed a decisive penalty to Leinster, much to the displeasure of the booing French fans, who felt that the Englishman already owed them two yellow cards.
Glorious sunshine had replaced the rain of the earlier in the day and Jonathan Sexton put Leinster on the board first from the kicking tee. But his effort was cancelled out by a penalty from opposite number Brock James to leave matters all-square at the end of the first quarter.
Leinster skipper Leo Cullen was lucky not to see yellow after landing a punch on Lionel Faure. If anything referee Barnes's decision to let Cullen off the hook was probably influenced more by theatrical manner in which the loosehead went to ground rather than the weak punch itself.
Clermont enjoyed a strong 15 minutes but their only reward was another penalty from James to which Sexton replied three minutes later.
But the French side were slowly but surely beginning to control the tempo of the game and were enjoying the lion's share of field position. Clermont finished the half the stronger of the two teams and two more penalties gave l'ASM a deserved six-point lead at the break.
Europe's defending champions started the second period in perfect fashion however as Kearney burst through a gap in the inside channel from Richardt Strauss's clever pass to set up a try for Healy.
Sexton's conversion put Leinster one point ahead before Kearney stunned Clermont when he slotted a long-range drop goal!
Almost immediately James had a chance to cut the lead to a single point but pushed his penalty attempt wide to awaken the ghosts of that fateful day in Dublin two years ago. The Australian didn't waver with his next kick though, leaving the scores at 16-15.
Sexton held his nerve to split the uprights from out wide going into the final quarter to restore the four-point gap as Leinster plied the pressure.
The closing stages were filled with drama and the TMO was called upon when Sexton sent a penalty attempt directly over the top of the outside upright. Leinster were denied the three points, setting up a grandstand finish as Clermont went in search of what would surely be a winning try.
Fofana and Clermont celebrated what they considered a five-pointer, but the video referee correctly ruled against them.
With just seconds left, Leinster survived a monumental final assault to advance to Twickenham after an epic battle.
Man of the match: The best full-back in Europe at the moment, Rob Kearney didn't put a foot wrong and produced a seven-minute spell that changed the complexion of the game.
Moment of the match: In an extraordinary finale, Fofana thought he had scored two minutes from time as he twisted out of Gordon D'Arcy's tackle, but as he landed on his elbow he lost his grip on the ball, which squirmed out of his hands as he tried to ground it.
Pens: James 5
Pens: Sexton 4
Clermont: 15 Lee Byrne, 14 Sitiveni Sivivatu, 13 Aurélien Rougerie, 12 Wesley Fofana, 11 Julien Malzieu, 10 Brock James, 9 Morgan Parra, 8 Elvis Vermeulen, 7 Alexandre Lapandry, 6 Julien Bonnaire, 5 Nathan Hines, 4 Jamie Cudmore, 3 Davit Zirakashvili, 2 Benjamin Kayser, 1 Lionel Faure.
Replacements: 16 Ti'i Paulo, 17 Vincent Debaty, 18 Daniel Kotze, 19 Julien Pierre, 20 Julien Bardy, 21 Ludovic Radoslavjevic , 22 Regan King, 23 Jean-Marcel Buttin.
Leinster: 15 Rob Kearney, 14 Isa Nacewa, 13 Brian O'Driscoll, 12 Gordon D'Arcy, 11 Luke Fitzgerald, 10 Jonathan Sexton, 9 Isaac Boss, 8 Jamie Heaslip, 7 Shane Jennings, 6 Sean O'Brien, 5 Brad Thorn, 4 Leo Cullen (c), 3 Mike Ross, 2 Richardt Strauss, 1 Cian Healy.
Replacements: 16 Sean Cronin, 17 Heinke van der Merwe, 18 Nathan White, 19 Devin Toner, 20 Kevin McLaughlin 21 Eoin Reddan, 22 Ian Madigan, 23 Fergus McFadden.
Venue: Stade Chaban-Delmas, Bordeaux
Referee: Wayne Barnes