Champions Cup holders Saracens have been drawn against Munster, Racing 92 and the Ospreys in next season's pool stages.
Saracens beat Munster at the semi-final stages in two of the last three Champions Cups, including last April as they won on to lift the trophy for a third time.
They meet in a difficult Pool 4, which also sees a return to Thomond Park for Simon Zebo and Donnacha Ryan.
Ireland full-back Zebo left Munster for Paris last summer after eight years with the Irish province, and is their joint-record tryscorer in the European Cup with 23.
Scotland full-back Stuart Hogg also makes a quick return to Scotstoun after his new club Exeter Chiefs were drawn with Glasgow Warriors. Sale Sharks and Top 14 finalists La Rochelle complete Pool 2.
Premiership rivals Bath and Harlequins will contest Pool 3 alongside Clermont Auvergne and Ulster, while four-time European champions Leinster are joined in Pool 1 by Lyon, Northampton, and Benetton.
Pool 5 sees Gloucester and Connacht take Top 14 on heavyweights Toulouse and Montpellier.
The pool stages begin in mid-November, two weeks after the Rugby World Cup final.
2019/20 Heineken Champions Cup draw
Pool 1: Leinster, Lyon, Northampton Saints, Benetton.
Pool 2: Exeter Chiefs, Glasgow Warriors, La Rochelle, Sale Sharks.
Pool 3: Clermont Auvergne, Ulster, Harlequins, Bath.
Pool 4: Saracens, Munster, Racing 92, Ospreys.
Pool 5: Toulouse, Gloucester, Connacht, Montpellier.