Billy Burns scored all of Gloucester's points as they claimed their place in the European Challenge Cup final with a tense 16-14 victory at La Rochelle.
La Rochelle were on a 15-match unbeaten run at the Stade Marcel-Deflandre, but that streak came to an end as Gloucester put up a remarkable display of defensive resilience.
David Humphreys' side's tackling was near immaculate in what was a ferocious encounter, Burns registering all of their points by converting his own try and kicking three penalties.
Their opponents dominated the ball with their powerful pack, but Gloucester did not give an inch.
Brock James, who had a poor game overall, kicked three penalties and replacement Damien Lagrange crossed the whitewash, but the Top 14 side could not convert their dominance into points.
It resulted in a famous Gloucester win and the Kingsholm outfit, who won this competition in both 2006 and 2016, can now look forward to facing either Stade Francais or Bath in the final at BT Murrayfield on May 12.
The two teams had met each other in the pool stages, with each winning on home soil. The Cherry and Whites knew they were in for a tough test, but they were handed an early advantage.
After Botia Veivuke charged towards Willi Heinz, La Rochelle lock Jone Qovu needlessly dropped a shoulder on the Gloucester captain at the ruck.
Qovu was rightly yellow carded by referee Andrew Brace, allowing Burns to put his team 3-0 up from the resulting penalty.
Burns then doubled the Gloucester lead when La Rochelle were penalised for not rolling away, but there was no let-up in the intensity of the encounter.
Arthur Retiere was an early replacement for Paul Jordaan in the home back line, while Botia was a constant menace.
James, on his 50th European appearance, then got La Rochelle on the board and Humphreys' team also went down to 14 before the break.
Tom Savage was harshly adjudged by Brace to have cleared out Botia with no arms at a ruck, allowing James to level as the teams went in at the break 6-6.
La Rochelle's tactics were clear - to try and bully Gloucester up front.
They went for the jugular, but the English side held firm with Ross Moriarty standing out in the week he was selected for this summer's British and Irish Lions tour to New Zealand.
Just before the hour mark, Burns put his team back ahead, before the game's crucial moment saw the fly-half intercept James' floated pass and sprint to the line from 70 metres.
Burns added the extras, but still La Rochelle refused to go away. James kicked a penalty and then missed with a long-range effort, before Lagrange powered over after a series of drives.
It was a score the French side deserved, but James missed the conversion.
It sent the game into the final 10 minutes with Gloucester two points clear and somehow they managed to hold on as James missed with late drop goal and penalty efforts.
