Leinster will once again face Ronan O'Gara's La Rochelle in the Champions Cup after the sides were drawn in the same group.
Leinster have faced La Rochelle in the last four seasons, and defeated La Rochelle in the group stages and the in the quarter-finals of last season's competition.
Leinster were beaten in two Champions Cup finals by La Rochelle in Marseille in 2022 and Aviva Stadium 2023 and lost to Toulouse in this year’s decider at the Tottenham Hotspur Stadium.
They were also drawn with Clermont, Benneton, and English sides Bristol and Bath in Pool 2.
Munster will also face familiar opposition in their group, with Northampton among the teams in their group.
Northampton defeated Munster in the group stages and the last 16 last season.
Also in Pool 3 with Munster is Saracens, the Bulls, Stade Francais and Castres.
Ulster will be joined in Pool 1 by last season's winners Toulouse, and Top 14 finalists Bordeaux. They will also be joined by the Sharks and English sides Exeter and Leicester.
Each club will play four matches against four different clubs, who are not from the same league, either home or away.
The pool stages kicks off in the first week of December. The final takes place in Cardiff on Saturday, May 24th.
In the Challenge Cup, Connacht have been grouped with Cardiff, Cheetahs, Perpignan, Lyon and Zebre in Pool 1.
Exact dates, venues and kick-off times will be announced in due course.
Pool One
Leicester
Toulouse
Bordeaux-Begles
Sharks
Exeter Chiefs
Ulster
Pool Two
Leinster
Clermont Auvergne
La Rochelle
Bristol
Benetton
Bath
Pool Three
Northampton
Munster
Bulls
Stade Francais
Saracens
Castres
Pool Four
Glasgow
Racing 92
Sale
Stormers
Toulon
Harlequins
