Leinster have been drawn with familiar foes La Rochelle for the 2025/26 Champions Cup.
The Irish province lost to Ronan O'Gara's side in the semi-finals in 2021 and the decider in the following two seasons but have had the upper hand since, winning the last three meetings.
Leo Cullen's men, semi-finalists last season, will also face Leicester Tigers, Harlequins and Bayonne in Pool 3, clubs from the same league being kept apart in the pool stages.
Two-time winners Munster will meet Bath, Toulon, Castres and Gloucester in Pool 2. They lost 16-14 in Castres in last year's pool stages.
First-time champions Bordeaux have been handed a rematch with losing finalists Northampton in Pool 4.
Fixtures will be announced later this month.
In the second-tier Challenge Cup, Connacht have been matched with Ospreys, Zebre, Montpellier, US Montauban and Georgia's Black Lion, while Ulster look to face a stiffer test with four games against Cheetahs, Cardiff, Exeter Chiefs, Racing 92 or Stade Francais.
Champions Cup
Pool 1: Toulouse, Clermont Auvergne, Sharks, Saracens, Glasgow Warriors, Sale.
Pool 2: Bath Rugby, RC Toulon, Munster Rugby, Castres Olympique, Edinburgh Rugby, Gloucester Rugby.
Pool 3: Leinster Rugby, Leicester Tigers, Harlequins, La Rochelle, Aviron Bayonnais, DHL Stormers.
Pool 4: Bordeaux Bègles, Scarlets, Bristol Bears, Section Paloise, Northampton Saints, Bulls.
Challenge Cup
Pool 1: Ospreys, Zebre Parma, Montpellier, US Montauban, Black Lion, Connacht Rugby
Pool 2: Lyon, Newcastle Falcons, Dragons RFC, Benetton, Lions, USAP
Pool 3: Toyota Cheetahs, Cardiff Rugby, Exeter Chiefs, Racing 92, Stade Francais, Ulster Rugby
