La Rochelle snatched a stunning 24-21 victory over favourites Leinster thanks to a last-minute try by Arthur Retiere after a monumental 10-minute goal-line assault in a superb European Champions Cup final in Marseille on Saturday.
Leinster had looked on course for a record-equalling fifth triumph as they heroically defended their line and a four-point lead for almost all of the final 10 minutes, only for Retiere to finally stretch over.
Johnny Sexton kicked six penalties and Ross Byrne added another as Leinster led throughout, despite a try in each half for the French side by Raymond Rhule and Pierre Bourgarit.
But La Rochelle, beaten in last year's final by Toulouse, backed themselves by turning down a succession of kickable penalties to hammer away through the forwards, and eventually got their reward - via a replacement wing.
It was an incredible finale to a hugely entertaining match as La Rochelle fully delivered on coach Ronan O'Gara's pre-match promise that his team "might not win, but we won't lose it."
Two Sexton penalties had Leinster ahead as they started with all their usual speed and energy but it was La Rochelle who claimed the first try when Dillyn Leyds off-loaded cleverly to fellow South African Rhule who then blasted clear to score.
La Rochelle had come into the game with a reputation as a power unit but they also showed plenty of creativity in attack and stretched Leinster all across the field in the first half.
However, their final pass accuracy faltered as they failed to turn positional dominance into points and Leinster survived and then earned another penalty that Sexton slotted for a 12-7 halftime lead.
La Rochelle ruined much of their good work with a succession of penalties, which were punished by Sexton as he edged the Irish province 18-10 ahead after an hour.
La Rochelle hit back though with a rolling maul try for Bourgarit and Ihaia West's difficult conversion made it a one-point game.
La Rochelle then looked to have imploded as Wiaan Liebenberg was sin-binned for a ludicrous trip on Jamison Gibson-Park and, with Sexton off injured, Byrne stepped up to slot the resulting penalty.
However, even down to 14 men, La Rochelle piled on the forward pressure but, declining four easy shots at goal, they could not breach Leinster's heroic goal-line defence as the clock ticked into the final minute.
They tried again and, perhaps helped by a slip which wrong-footed the defence, it was replacement wing Retiere who stretched out an arm through the smallest of gaps to send the yellow flag-waving hordes into raptures.
West landed the conversion and the whistle sounded to complete a French European double after Lyon won the Challenge Cup on Friday.
"We are a big team, a power team, and that last 10 minutes showed what this shirt and town mean to us," said La Rochelle lock Will Skelton. "I don't know how long we are going to party, but it will be a good time in the port."
Sexton said: "We weren't at our best. 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."