La Rochelle earned a convincing 32-23 victory over Leinster at Stade Marcel Deflandre to reach their first European Champions Cup final.
The French side, who had never previously made it as far as the last four, will now face fellow Top 14 club Toulouse at Twickenham on May 22.
Leinster have won the competition on four previous occasions and started Sunday's contest brightly through Tadhg Furlong's eighth-minute try.
The hosts were a man short at that point after Wiaan Liebenberg was sin-binned for an offside infringement, but they hit back thanks to a penalty and drop goal from Ihaia West.
West was successful from a couple more kicks before half-time, but only after Ross Byrne had added six points from the boot for Leinster in a tightly-contested opening period that ended with the visitors ahead by one.
That kicking battle ensued in the early stages of the second period when Byrne responded to West edging La Rochelle in front for the first time in the contest.
Leinster were a point to the good at that point but lost James Lowe to a yellow card for not rolling away in what proved to be a pivotal moment in an entertaining clash.
West split the sticks once more to restore his side's advantage and Gregory Alldritt found a way over the line 15 minutes from time, which West inevitably added to with the extras.
La Rochelle pushed for another try to seal the win and they found it as Will Skelton broke away from the driving maul to start the celebrations.
Byrne had the final say in terms of the scoring by finding a gap and dotting down late on, but La Rochelle comfortably held on to set up an all-French final at Twickenham.
ILS L'ONT FAIT !!! LES JAUNE ET NOIR S'ENVOLENT POUR LA PREMIÈRE FINALE DE CHAMPIONS CUP DE LEUR HISTOIRE EN S'IMPOSANT 32 À 23 FACE AU @leinsterrugby !!!! #SRvLEI #ChampionsCup #FievreSR pic.twitter.com/anv5PXEvWl— Stade Rochelais (@staderochelais) May 2, 2021