The Tigers rescued their Heineken Cup campaign from the perils of possible pool stage elimination by staging a superb second-half fightback to win 23-19 against the French heavyweights.
Leicester, European champions in 2001 and 2002, appeared to have little chance of progressing from Pool Four when Clermont cruised into a nine-point interval lead at Welford Road.
But Leicester rapidly wiped out that deficit before Toby Flood's 62nd and 72nd-minute penalties secured the points and kept Tigers on course for an 11th quarter-final appearance in 15 seasons of Heineken Cup rugby.
England centre Manu Tuilagi and flanker Julian Salvi scored tries for the home side, while Flood kicked 13 points to put Leicester above Clermont in the group and just behind leaders Ulster.
Ex-New Zealand wing Sitiveni Sivivatu touched down for Clermont, while Morgan Parra and David Skrela both dropped goals, with Parra also slotting two penalties and a conversion.
Ulster pressed home their ambitions with a bonus-point 46-20 victory over Aironi in Monza.
Brian McLaughlin's men scored six tries on their way to a well-merited win, which puts them in pole position at the top of Pool Four ahead of next month's crunch clashes at home against Leicester and away to Clermont Auvergne.
Andrew Trimble, Tom Court, Craig Gilroy and replacements Robbie Diack and Adam Macklin were all on the mark for the visitors, while a first-half penalty try added to Italian woes.
George Biagi, Roberto Quartaroli and Sinoti Sinoti scored tries for Aironi.
Leinster delivered a performance worthy of champions as Bath's faint hopes of progressing from Pool Three were finally ended at a packed Aviva Stadium in Dublin.
The West Country side had run the Irishmen close six days previously but this time had no answer to their opponents' pace and precision as they lost 52-27.
Leinster could even afford to lose skipper Leo Cullen to the sin-bin in the first half - and still score 14 unanswered points.
The bonus point was secured just 30 seconds into the second half as Luke Fitzgerald sprinted half the length of the field to score his second try.
Ireland fly-half Jonathan Sexton finished with 20 points from a try, dropped goal and six conversions and Leinster's other scorers were Rob Kearney, Eoin Reddan, Rhys Ruddock and Ian Madigan.
Isa Nacewa also kicked a conversion.
Stephen Donald, Dave Attwood and Ben Williams grabbed late tries for Bath and Olly Barkley kicked three conversions and two penalties.
Also in Pool Three, Rory Lamont marked his return to Scottish rugby with Glasgow's only try in the 13-13 draw against Montpellier in France which kept his side's slim hopes of a quarter-final place alive.
The 29-year-old, who has been capped 26 times by Scotland, crossed for the Warriors' second-half try in only his second game back in Scottish rugby after the frustration of his recent spell in France with Toulon.
Replacement scrum-half Benoit Paillaugue, who stepped up for a late penalty instead of Francois Trinh-duc, sliced the last kick of the game and blew the chance to give Montpellier, who bagged a try through Yohan Audrin, victory.
An excellent 75th-minute try from Jonny May kept alive Gloucester's faint Pool Six hopes with a narrow 23-19 victory over Connacht.
Niall O'Connor looked to have earned Connacht their first win of the competition when his 72nd-minute penalty put the visitors 19-16 up, but replacement centre May then sailed past two defenders for the decisive score.
Tiernan O'Halloran and Tim Taylor had earlier traded first-half tries while O'Connor kicked four penalties and Taylor and Freddie Burns combined for three for the hosts.
London Irish gave themselves a mountain to climb if they are to qualify for the quarter-finals after Racing Metro bounced back from their loss in Paris last week with a 25-19 Pool Two victory in Reading.
Racing wing Sereli Bobo crossed for a try and fly-half Jonathan Wisniewski kicked 20 points with three penalties, three drop goals and a conversion to settle the clash.
Hooker David Paice got a try for London Irish with the last move of the game and wing Tom Homer kicked 14 points with four penalties and a conversion, but the hosts fell short.
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