Champions Cup holders Saracens will face Top 14 winners Clermont Auvergne, Ospreys and Northampton Saints in next season's pool stages.
Sarries defeated Clermont 28-17 in last month's final at Murrayfield to become the fourth side to win back-to-back titles. They will meet again in a highly competitive Pool 2.
Aviva Premiership champions Exeter Chiefs have also been handed a difficult draw. They will face Montpellier, Glasgow Warriors and three-time winners Leinster in Pool 3.
For the second successive season Munster, Racing 92 and Leicester Tigers will meet in the pool stages, with Castres completing Pool 4.
Guinness PRO12 winners Scarlets have been drawn with former winners Toulon and Bath, as well as Benetton Treviso, with English duo Wasps and Harlequins in Pool 1 along with La Rochelle and Ulster.
In the Challenge Cup, Edinburgh and London Irish will face defending champions Stade Francais in Pool 4.
Five-time European Cup winners Toulouse are in Pool 2 along with Cardiff Blues, Sale Sharks and Lyon, while Challenge Cup runners-up Gloucester will play Pau, Zebre and Agen.
Next season's Challenge and Champions Cup finals will be played at Bilbao's Sam Mames Stadium on May 11 and 12, 2018 respectively.
2017/18 Champions Cup draw
Pool 1: Wasps, La Rochelle, UIster, Harlequins.
Pool 2: Clermont Auvergne, Saracens, Ospreys, Northampton Saints.
Pool 3: Exeter Chiefs, Leinster, Montpellier, Glasgow Warriors.
Pool 4: Munster, Racing 92, Leicester Tigers, Castres.
Pool 5: Scarlets, Toulon, Bath, Benetton Treviso.
2017/18 Challenge Cup draw
Pool 1: Newcastle Falcons, Newport Gwent Dragons, Bordeaux-Begles, Enisiei-STM.
Pool 2: Cardiff Blues, Sale Sharks, Lyon, Toulouse.
Pool 3: Gloucester, Pau, Zebre, Agen.
Pool 4: Stade Francais, Edinburgh, London Irish, Krasny Yar.
Pool 5: Brive, Connacht, Worcester Warriors, Oyonnax.
Round one to be played on the weekend of October 12-15