Leinster will join Bath, Wasps and European Champions Cup holders and Paul O'Connell's new side Toulon in a real heavyweight pool in next season's competition.
The Aviva Premiership pair were drawn in Pool Five of the 2015-16 competition and there were gasps at the draw in the Neuchatel auditorium in Switzerland when Toulon and Leinster joined them.
Big spending Toulon have been champions of Europe for the last three years and beat fellow French club Clermont-Auvergne in the final of last season's competition at Twickenham.
Leinster have also been champions of Europe three times and ended Bath's interest in the competition at the quarter-final stage last term before succumbing to Toulon in the semi-final.
Aviva Premiership champions Saracens also have a tough draw in Pool One, where they have Ulster, four-time European kings Toulouse and French newcomers Oyonnax for company.
Clermont's attempt to go one better next season will be tested at the group stage by Welsh region Ospreys and Aviva Premiership side Exeter Chiefs.
They are joined in Pool Two by French side Bordeaux-Begles, who came through the play-offs to book their Champions Cup place.
Munster were drawn with two-time European champions Leicester in Pool Four alongside French champions Stade Francais.
The trio will seek to take advantage of Benetton Treviso - the only Italian side in the competition - being in their section.
Northampton were paired alongside PRO12 champions Glasgow, French side Racing 92 and Welsh outfit Scarlets in Pool Three.
European Professional Club Rugby confirmed at the draw that next season's Champions Cup final will take place at the Grand Stade de Lyon on May 14, with the Challenge Cup final played at the same venue the previous day.
It was also confirmed that the two competitions' 2017 finals will be played at Murrayfield Stadium in Edinburgh.