Munster overturned a 19-point deficit to claim a famous victory over Clermont Auvergne in France.
Johann Van Graan's men became only the second side to win at Stade Marcel Michelin in the Champions Cup to continue their unbeaten start to the season.
The French side looked en route to a bonus-point win following a blistering start which brought them tries from Alivereti Raka, Damian Penaud, Etienne Fourcade and a penalty try inside the opening 23 minutes.
But 24 points from the boot of JJ Hanrahan and scores from Mike Haley and CJ Stander completed a remarkable fightback to put Munster on course for the knockout stages, before Kevin O’Byrne sealed one of the province’s greatest European nights.
Clermont, seeking a 32nd win in 33 home matches in the pool stages, powered into the lead after only 26 seconds.
Keith Earls spilled the kick-off into the hands of second row Peceli Yato, who produced a fierce hand-off on Gavin Coombes before he offloaded to Raka.
The France international charged onto the ball and crossed the line unchallenged to score, and Camille Lopez converted for a 7-0 lead.
Munster out-half Hanrahan steadied the ship with a penalty but another error from the restart compounded their dire start.
After a succession of attacks around the ruck, Lopez looked to exploit the overlap to send Penaud in at the corner, only to be denied by a desperate Shane Daly.
The winger deliberately knocked the ball on to deny a certain try, but his actions resulted in a penalty try and ten minutes in the sin bin to tarnish his full European debut.
The French side made their man advantage pay after Hanrahan had added a second penalty for Munster.
Lopez shifted the ball to the outside where Raka looped a long pass to Penaud, who strolled in at the corner, and Lopez added the extras to make it 21-6 after only 15 minutes.
Hanrahan was on target again to chip away at the lead but Clermont secured the bonus point after 23 minutes when Fourcade fed a lineout and latched onto the rolling maul to score.
Lopez converted again and at 28-9 the result looked to be secured, but Munster gave themselves a glimmer of hope when Haley scythed through to score.
Hanrahan converted to cut the gap to 28-16 at half-time.
The Munster No 10 then narrowed the deficit to six points with a pair of penalties after the restart as the Irish side edged their way back into the contest.
The lead was down to three after 57 minutes thanks to a sixth Hanrahan penalty after Judicael Cancoriet was sin-binned for a no-arms hit on Munster hooker Rhys Marshall.
Lopez restored the six-point lead with a penalty of his own but Thibault Lanen opened the door for the visitors again when he saw yellow for pulling down Tadhg Beirne at a lineout.
And this time they took their opportunity to complete the comeback as Stander barged over at the back of a maul after a five-metre lineout, and Hanrahan held his nerve to convert and make it 32-21.
Replacement hooker O'Byrne then sealed the unlikeliest of victories when he crashed over late on, with Hanrahan maintaining his perfect record off the tee.