Three-time champion Leinster was consigned to a record home defeat in its European Champions Cup opener on Monday (AEDT) as Bath secured an impressive 33-6 victory in Dublin.
The RDS Arena has become a fortress for Leinster, but last season's semi-finalist was no match for Premiership side Wasps in Pool Five on Sunday as the Pro12 outfit suffered its biggest home loss in European competition.
Ruaridh Jackson and Jonny Sexton traded penalties in a tense first quarter, but it was Wasps who took charge with a commanding display on the road.
Elliot Daly booted a 50-metre penalty before the rapid Christian Wade took advantage of poor defending from Dave Kearney to score the first try of the game and Jackson converted to put the visitor 16-6 up at the break.
Wasps must have been braced for a Leinster onslaught in the second half, but Dai Young's side pressed home its advantage and Joe Simpson raced away to claim Wasps' second try.
Leinster also lost forwards Richardt Strauss, Sean O'Brien and Mike McCarthy to injury on a miserable day, which was capped off when man of the match Charles Piutau went over in the corner.
Alex Lozowski converted that late score from the touchline to add to Jackson's 13 points with the boot on a memorable day for Wasps.
Dan Biggar inspired Ospreys to a 25-13 victory over Exeter Chiefs in the only other Champions Cup fixture of the day in Pool Two.
The Wales fly-half booted 20 points and Josh Matavesi claimed the home side's solitary try nine minutes from time as Ospreys claimed a morale-boosting victory after making a poor start to their Pro12 campaign.
James Short claimed the only try of the first half as the Chiefs led 10-6 at the break, but the visitor was second best after the interval.
The Pool Five match between Toulon and Bath and Bordeaux-Begles' Pool Two game against Clermont Auvergne were postponed after the horrific attacks in Paris on Saturday (AEDT).