Leinster booked their third Heineken Cup Final when they beat Clermont Auvergne 15-19 Bordeaux France at Stade Chaban-Delmas.
Leinster won an extraordinary match which finished with a titanic push for the tryline by Clermont and even had a Wesley Fofana try not awarded.
Leinster who were trailing 12-6 at half time will face Ulster in the final at Twickenham in London England.
The Irish visitors enjoyed a five minute spell early in the second half in which they took the lead from Clermont and once they were ahead they defended their lead.
Clermont owned the final 10 minutes but Leinster defence within their 25 was immense.
Fofana found a gap and went over to score but was unable to put the ball down and the try decision went to the TMO who had an easy call.
By reaching the final Leinster have set up the first all-Irish Heineken Cup final as they will play fellow Irish club Ulster.
Leinster scored the one try of the match - through Cian Healy - and had to show extraordinary defensive pluck at the end as Clermont, who were in the last four for the first time, battered away on their line.
However, the Irishmen held on and can emulate Leicester (2001/02) in being the only other side to defend their title when they play Ulster at Twickenham on May 19.
Leinster coach Joe Schmidt praised his players for managing to defy Clermont at the end.
"Everyone can see that it was really tough from start to finish," said the Kiwi, who was assistant coach at Clermont till 2010 when they finally won the French title.
"The guys didn't hold back in putting their bodies on the line when Clermont attacked in the final few minutes. We can be very proud of winning a game such as this."
Clermont counterpart Vern Cotter admitted it would be painful viewing watching the match again but said his side were still lacking that cutting edge at this level.
"I am really disappointed. So much effort and no reward at the end," said the 50-year-old New Zealander, who has been at the club since 2006.
"In the last five minutes I sensed the real hunger of the players and they showed enormous character. Even if we lost, there are interesting things to take out of this. We still have to work on some things in order to move up another step."
Leinster opened the scoring with an early penalty from Jonathan Sexton and Clermont suffered a blow in the 13th minute when Julien Malzieu, scorer of three tries in their quarter-final meeting two years ago, had to be replaced by Jean-Marcel Buttin.
Brock James levelled in the 18th minute with a penalty from in front of the posts as Clermont produced some incisive attacking rugby that had their opponents on the back foot.
However, every time they made inroads into the Leinster 22 they were penalised by referee Wayne Barnes, not always to the delight of the thousands of Clermont fans that had made the trip.
Barnes further incurred their displeasure when he failed to penalise Leinster captain Leo Cullen in the 22nd minute after the lock punched Clermont prop Lionel Faure.
The latter's theatrical collapse to the ground may have swayed the referee in the Irishman's favour.
Clermont edged ahead in the 32nd minute as James landed a second penalty only for Sexton to make it 6-6 two minutes later with a penalty of his own.
James restored the French side's lead three minutes from the break with a penalty and added another for good measure on the stroke of half-time to send Clermont in 12-6 ahead.
However, Leinster came out a different side in the second-half and stormed into the lead through a brilliantly worked try.
Hooker Richard Strauss released Rob Kearney, who tore through the Clermont defence and passed to Healy, who rumbled over the line to touch down.
Sexton converted for 13-12 and the Irish side extended their lead in the 48th minute with a stunning drop goal by Kearney from just inside the Clermont half for 16-12.
James reduced the deficit with a penalty in the 53rd minute but Sexton made it 19-15 with 17 minutes remaining.
In a dramatic finale, Clermont thought they had secured victory.
However star French centre Wesley Fofana lost control of the ball as he attempted to ground it over the line and the French side's celebrations were brought to a juddering halt when the video referee told Barnes it was not a try.
Undeterred the French side laid siege to the Leinster line with a succession of penalties going their way but sterling Irish defence thwarted them.
The valiant attempts by the French finally came to nothing as Barnes whistled for a penalty in Leinster's favour and Sexton kicked it over the deadball line.
Final Score Clermont Auvergne 15 (12) Leinster 19 (6)
Penalties: James 5
Penalties: Sexton 3
Referee: Wayne Barnes (England)
Assistant Referees: Nigel Owens (Wales), David Pearson (England)
TMO: Geoff Warren (England)
Citing Commissioner: Rob Flockhart (Scotland)
ASM Clermont Auvergne: L Byrne; S Sivivatu, A Rougerie [capt], W Fofana, J Malzieu; B James, M Parra; L Faure, B Kayser, D Zirakashvili, J Cudmore, N Hines, J Bonnaire, A Lapandry, E Vermeulen
Replacements: T Paulo, V Debaty, D Kotze, J Pierre, J Bardy, L Radoslavjevic , R King, J Buttin
Leinster: R Kearney; I Nacewa, B O'Driscoll, G D'Arcy, L Fitzgerald; J Sexton, I Boss; C Healy, R Strauss, M Ross, L Cullen [capt], B Thorn, S O'Brien, S Jennings, J Heaslip
Replacements: S Cronin, H Van der Merwe, N White, D Toner, K McLaughlin, E Reddan, I Madigan, F McFadden