French heavyweights Clermont Auvergne were given a major fright by the Ospreys before claiming a 26-21 European Champions Cup victory at the Liberty Stadium.
The Welsh side, beaten five times already this season in Guinness PRO14 action, looked down and out following early Clermont tries for wing Alivereti Raka and full-back Scott Spedding.
Scrum-half Morgan Parra converted both touchdowns and kicked two penalties to secure a comfortable half-time advantage, then completed his penalty hat-trick early in the second period.
Parra's opposite number Rhys Webb claimed an 18th-minute try for the Ospreys that his half-back partner Dan Biggar converted, but the home side dominated a second period that saw full-back Dan Evans collect two touchdowns and Biggar add further conversions.
Ultimately, the Ospreys had to settle for a losing bonus point, but it was a valiant effort that did not look like materialising when they trailed by 14 points after 10 minutes.
While Clermont's December home and away fixtures against reigning European champions Saracens seem set to decide Pool Two, the Ospreys, who travel to Allianz Park next Saturday, can take heart from a gutsy performance.
Wales head coach Warren Gatland looked on as Ospreys produced some impressive rugby in patches, yet Clermont - runners-up in three of the past five top-flight European finals - had just enough left in the tank, with Spedding's long-range penalty securing victory a minute from time.
Clermont wasted no time getting into their stride as they launched a number of powerful ball-carriers at the Ospreys from kick-off, and they struck with a fourth-minute try that owed everything to their power game.
The Ospreys struggled to make first-up tackles count, and Raka showcased considerable brute-strength as he barged his way over from 20 metres out, with Parra's conversion making it 7-0 inside five minutes.
And matters deteriorated for the home side from Clermont's next attack, as their forwards once again built an imposing platform and Spedding sliced through for an all-too-easy try that Parra converted.
It was a nightmare start for the Ospreys, who were unbeaten in 15 previous European games against French opposition at the Liberty Stadium, and, even when wing Keelan Giles sprinted clear for what looked like an opening score, it was disallowed following midfield obstruction by his team-mate Kieron Fonotia.
The Ospreys, though, impressively regrouped, and a period of pressure near Clermont's line was rewarded when Wales international Webb pounced from close range and Biggar's conversion halved the deficit.
But Clermont quickly replied through two Parra penalties during a dominant five-minute spell, and the Ospreys were effectively back to square one, trailing by 13 points midway through the second quarter.
The Ospreys then saw number eight Dan Baker depart the action on a stretcher following a back-of-the-lineout collision that ended with him falling awkwardly. He was replaced by Olly Cracknell.
Effectively needing to score next if they wanted to stay in the contest, Ospreys began the second period in determined fashion, and they gained an immediate temporary numerical advantage when Clermont wing David Strettle was sin-binned for deliberate offside deep inside his own 22.
Parra kicked a penalty while Strettle was off, only for the Ospreys to give themselves a glimmer of hope when Evans touched down wide out and Biggar booted the touchline conversion, making it 23-14.
Evans' second try set up a thrilling finish, but Spedding closed out the game and it was a case of what might have been for the Ospreys.