Paris - Saracens face a tough defence of their European Champions Cup title after being drawn alongside French heavyweights Toulon in the pool stages of the 2016/17 tournament.
Scarlets, the sole Welsh team in the Champions draw, and Saracens' English Premiership rivals Sale make up Pool 3.
Only the winners of each of the five pools are guaranteed a place in the quarter-finals, along with the three best second-placed finishers.
Last season's beaten finalists and French champions, Dan Carter's Racing 92, are drawn in a tough Pool 1 alongside Glasgow, Leicester and Munster.
Pool 2 features Connacht, last season's semi-finalists Wasps, Toulouse and Italian outfit Zebre, traditionally the whipping boys of the continent's showpiece club competition.
Reigning Challenge Cup champions Montpellier are drawn in what looks like to be a testing Pool 4 with Leinster, Northampton and Top 14 rivals Castres.
Clermont, finalists in 2013 and 2015, are also handed a tough draw in Pool 5, aligned with Exeter, Ulster and Bordeaux-Begles.
The first round of matches takes place on the weekend of October 15, with the final scheduled for Edinburgh on May 13.
European Champions Cup
Pool 1: Racing 92 (FRA), Glasgow Warriors (SCO), Leicester Tigers (ENG), Munster Rugby (IRL)
Pool 2: Connacht Rugby (IRL), Wasps (ENG), Toulouse (FRA), Zebre (ITA)
Pool 3: Saracens (ENG), RC Toulon (FRA), Scarlets (WAL), Sale Sharks (ENG)
Pool 4: Leinster Rugby (IRL), Montpellier (FRA), Northampton Saints (ENG), Castres Olympique (FRA)
Pool 5: Exeter Chiefs (ENG), ASM Clermont Auvergne (FRA), Ulster Rugby (IRL), Bordeaux-Begles (FRA)
European Challenge Cup
Pool 1: La Rochelle (FRA), Gloucester Rugby (ENG), Benetton Treviso (ITA), Bayonne (FRA)
Pool 2: Ospreys (WAL), Grenoble (FRA), Newcastle Falcons (ENG), Lyon (FRA)
Pool 3: Brive (FRA), Worcester Warriors (ENG), Newport-Gwent Dragons (WAL), Enisei STM (RUS)
Pool 4: Cardiff Blues (WAL), Bath Rugby (ENG), Pau (FRA), Bristol Rugby (ENG)
Pool 5: Harlequins (ENG), Edinburgh Rugby (SCO), Stade Francais Paris (FRA), Timisoara Saracens (ROM)
European rugby weekends, 2016/17
Round 1: October 13/14/15/16
Round 2: October 20/21/22/23
Round 3: December 8/9/10/11
Round 4: December 15/16/17/18
Round 5: January 12/13/14/15
Round 6: January 19/20/21/22
Quarter-finals: March 30/31-April 1/2
Semi-finals: April 21/22/23
Finals, Edinburgh's Murrayfield Stadium: Challenge Cup May 12; Champions Cup May 13