Munster had reached the tournament's knockout stages every year since 1998, also losing three semi-finals and two quarter-finals, so it was possibly a case of now or never for captain Anthony Foley and his battle-hardened warriors.
Well over two thirds of a capacity 74,500 crowd roared Munster home, although Biarritz did everything they could to spoil the party.
First-half tries by South African centre Trevor Halstead and Irish international scrum-half Peter Stringer put Munster in the driving seat after Biarritz wing Sereli Bobo's third-minute touchdown set the tone for a fast-flowing spectacle.
There was an inevitable goalkicking exchange between British & Irish Lion Ronan O'Gara and Dimitri Yachvili, which the Biarritz scrum-half shaded 14-13 on points, but Munster - inspired by the dynamic Stringer - consistently kept their noses in front.
Biarritz challenged the favourites in every area, especially the lineout, yet hopes of emulating previous French European Cup winners Toulouse and Brive were ultimately dashed by Munster's unbreakable spirit and unrelenting commitment.
Neither side, exhausted by the game's punishing physicality, could produce a try in the second period, and a 74th-minute O'Gara penalty - neither he nor Yachvili missed a kick from 10 shots at goal between them - sealed the deal.
The Irish hordes were silenced within three minutes as a much-vaunted Biarritz back division made their mark in scintillating style.
Unlike during their respective quarter-final and semi-final victories over Sale Sharks and Bath, Biarritz sought early width, which brought a sparkling reward when centre Philippe Bidabe brushed off John Kelly's weak tackle to send Bobo scampering over.
Yachvili's effortless conversion secured a 7-0 lead, before an opening O'Gara penalty strike narrowed the deficit.
It all meant a pulsating start and Biarritz were in no mood to allow Munster's juggernaut pack any threat of early physical dominance.
When Munster secured promising field positions, twice they opted for touch from 30 metres out instead of going for three points. But their tactics reaped a rich reward as a breathless opening quarter neared its conclusion.
The Biarritz defence, unbreachable against Sale and Bath, cracked on 17 minutes when repeatedly recycled possession eventually resulted in Halstead smashing his way across for a try which O'Gara converted from the touchline.
A Yachvili penalty drew Biarritz level, and with both defences being consistently pummelled, there seemed little doubt that a stamina-sapping contest would take a punishing toll.
Biarritz, expertly mixing their attacking game, were comfortable with ball in hand, but Munster stung them with a sucker-punch try eight minutes before the break.
Munster looked to have their hands full making ground from set-piece ball 20 metres out, yet the Biarritz defence went absent without leave and a disbelieving Stringer sniped unmarked up the blindside, celebrating his try with a belly-flop dive.
O'Gara converted, and then kicked a penalty three minutes into the second period to put Munster 10 points clear.
Biarritz needed a foothold in the Munster half, and two Yachvili penalties during a three-minute spell suddenly threatened a French revival.
The unflappable Yachvili slotted his fourth successful penalty 10 minutes from time, setting up a nerve-shredding climax for Munster fans who thought their team were home and dry at 20-10 ahead.