Heineken Cup runners-up Saracens and two-time winners Leicester Tigers have been handed tough draws in the inaugural European Rugby Champions Cup.
Sarries, beaten by Toulon in the Heineken Cup final, are in Pool One alongside Munster, Clermont Auvergne and Sale Sharks.
Leicester meet Toulon, Ulster and Scarlets in Pool Three.
The competition, replacing the Heineken Cup, features five four-team groups.
The pool winners and three best runners-up will secure quarter-final places.
In Munster, Saracens face two-time Heineken Cup winners, while Clermont were beaten finalists in 2013 before reaching the semi-finals this year.
English champions Northampton initially missed out on being a top seed, but were placed among the Tier One teams after beating Glasgow Warriors and Castres in a pre-draw.
They will face Racing Metro, Ospreys and Treviso in Pool Five, while Bath meet four-time Heineken Cup champions Toulouse, Montpellier and Glasgow Warriors in Pool Four.
Harlequins are in Pool Two alongside Leinster, Castres and Wasps.
In the draw for the second-tier European Rugby Challenge Cup, London Irish were drawn alongside Cardiff Blues, Grenoble and a qualifier in the stand-out pool.
The new competitions were confirmed in April, after almost two years of negotiations.
English clubs, in particular, had long advocated change to the organisation of European rugby.
European Rugby Champions Cup draw:
Pool One: Saracens, Munster, Clermont Auvergne, Sale Sharks.
Pool Two: Leinster, Castres, Harlequins, London Wasps.
Pool Three: Toulon, Leicester Tigers, Ulster, Scarlets.
Pool Four: Glasgow Warriors, Montpellier, Bath, Toulouse.
Pool Five: Northampton Saints, Racing Metro, Ospreys, Benetton Treviso.
European Rugby Challenge Cup draw:
Pool One: Cardiff Blues, London Irish, Grenoble, Qualifier.
Pool Two: Exeter Chiefs, Bayonne, Connacht Rugby, La Rochelle.
Pool Three: Stade Francais Paris, Newport Gwent Dragons, Newcastle Falcons, Qualifier.
Pool Four: Edinburgh, Begles Bordeaux, London Welsh, Lyon.
Pool Five: Gloucester, Brive, Zebre, Oyonnax.