A courageous Leinster fightback proved in vain as Clermont Auvergne claimed a 27-22 victory in Lyon to set up a European Champions Cup final meeting with holders Saracens.
Franck Azema's men racked up 15 unanswered points in as many minutes at the start of Sunday's match, David Strettle playing a starring role as the wing scored one try and set up another either side of being the victim of a cynical pull that earned Leinster skipper Isa Nacewa a yellow card.
However, three-time European champions Leinster came roaring back - Jonathan Sexton kicking four penalties - and looked to have claimed the lead through Dan Leavy, only for the try to be chalked off due to the scorer having infringed inside his own half.
That decision halted Leinster's momentum and Camille Lopez found the target with two drop goals as Clermont finished strongly to seal victory despite a stunning individual try from Garry Ringrose.
Beaten finalists in 2013 and 2015, Clermont will now hope to make it third time lucky in their bid to earn a first European title when they face Saracens at Murrayfield on May 13.
Leinster were left with a mountain to climb after making a woeful start at a predictably loud Stade de Gerland.
Strettle's perfectly weighted chip set up a third-minute try for Peceli Yato, which was converted by Morgan Parra.
The visitors were then reduced to 14 men when Nacewa was sin-binned for pulling back Strettle as the wing looked to support the run of Scott Spedding.
Parra kicked the resulting penalty and produced a wonderful cut-out pass five minutes later to put Strettle over on the right flank, with Leinster in disarray.
The Irish province belatedly rallied, though, and were given a lifeline at the end of the first half. Parra pushed a 38th-minute penalty that would have stretched Clermont's lead to 18 points and Sexton then kicked his side's first points to make it 15-3 at the interval.
When Sexton split the posts on three further occasions early in the second period, Clermont were looking alarmingly vulnerable in the face of mounting pressure from their opponents.
Then came the match-turning moment as Leavy went over at the end of a flowing Leinster break, only to be penalised when replays showed he had held the leg of Aurelien Rougerie at a ruck.
Parra kicked the resulting penalty and Lopez's first drop goal put Clermont nine clear, but Ringrose responded with a spectacular solo try from inside his own half that set up a grandstand finish.
Clermont were grateful when the influential Lopez followed a 71st-minute penalty with another accurate drop goal, ensuring a late three-pointer for Sexton proved in vain.