Arthur Retiere scored the decisive try to help La Rochelle to a nail-biting 24-21 win over four-time champions Leinster in a thunderous Champions Cup final in Marseille on Saturday.
Leinster captain Johnny Sexton kicked six penalties and Ross Byrne one as La Rochelle paid for their ill-discipline.
But the French side kept themselves in the game with three tries, all converted by Ihaia West.
Springbok winger Raymond Rhule crossed in the first half before Pierre Bougarit was driven over to set up a monumental final 15 minutes at the end of which Retiere darted over from close range to seal La Rochelle's maiden Cup victory.
For La Rochelle's head coach Ronan O'Gara -- who won it twice as a player with Munster -- it was an emotional moment.
"This is important for my family, I am very emotional as my mother is not well and was unable to be here," said the 45-year-old Irishman.
"This is for her."
Sexton was hurt by the defeat.
"We weren't at our best," he told BT Sport. "We will have to look at it before we point any fingers. It is devastating.
"Fair play to La Rochelle, they came here with a plan. I didn't see them coming back but we did not clear our lines and we paid the price."
The omens didn't look good as La Rochelle gave away four penalties in the opening eight minutes of play at the Stade Velodrome, Sexton kicking two of them.
The Top 14 side roared straight back into the game, however, Dillyn Leyds drawing two defenders and offloading smartly to fellow Springbok winger Rhule.
The Ghana-born Rhule, who admitted in the week that unlike most rugby players he didn't like running, the gym or stretching, proceded to show a fine pair of heels to swerve past last defender Hugo Keenan for a well-taken try, converted by Kiwi fly-half West.
Another infringement saw Sexton nail his third penalty to hand Leinster the lead once more.
The game then turned into one of attrition fought out between the two 22m areas.
La Rochelle deployed giant Australian lock Will Skelton and France's Kiwi-born prop Uini Atonio to devastating effect, while Leinster centre Garry Ringrose put in a number of quality tackles outwide.
West spurned a long-range shot at goal to go for the corner, but a dropped pass by Jeremy Sinzelle saw a try go a-begging.
Leinster had strayed offside and an attacking scrum was set, with the French team in the ascendancy.
Dany Priso was penalised for bringing the set piece down, however, and the Irish province breathed again.
From the ensuing line-out and maul, Jimmy O'Brien chipped ahead and Dulin inexplicably tried to run the ball out from behind his own line but was caught by Jamison Gibson-Park, handing Leinster a five-metre scrum.
La Rochelle stood firm, but ended the half as they started it, straying offside to hand Sexton a simple fourth penalty in front of the posts to leave it 12-7.
West kicked his first penalty just a minute into the second period, Sexton responding with two more of his own as English referee Wayne Barnes punished La Rochelle for persistently straying offside.
West went to the corner on his next opportunity and it paid off as La Rochelle produced a perfect rolling maul off their attacking lineout, hooker Bougarit at the bottom of a pile of bodies that breached the Leinster line.
The Kiwi converted to pull his side up to within one point of Leinster.
But once again La Rochelle pushed the self-destruct button, Thomas Lavault yellow carded for a needless trip on Gibson-Park, Byrne kicking the resulting penalty with 15 minutes to play.
Fatigue set in as the players wilted in the stifling Velodrome, with a crowd of 59,682 basking in temperatures of 28 degrees Celsius (82F).
Twice West opted for scrums rather than kickable penalties and twice Leinster resisted in an extraordinarily bruising battle of wills.
But the 'Blue Wall' was finally breached, Retiere crossing after a dozen pick-and-gos, bodies littered around the pitch after a monumental defensive battle.