The Heineken Champions Cup will return to a multi-pool format next season.
Tournament organisers have scrapped two groups of 12 system, with the 24 qualifiers now featuring in four pools, each containing six teams.
There will be a maximum of two clubs from the same league – Gallagher Premiership, United Rugby Championship and French Top 14 – in each pool.
And there are no matches between clubs from the same league. Each team will play four games against four different clubs who are not from the same league, either home or away, during the pool stage.
The leading four clubs in each pool will qualify for the round of 16, and each fifth-placed team progress to the European Challenge Cup knockout phase.
The Challenge Cup will comprise 18 teams in three pools of six, with games in both tournaments being played over eight weekends and culminating in finals at Tottenham Hotspur Stadium next May.
European Professional Club Rugby chairman Dominic McKay said: “Our focus has always been to ensure that everyone can easily understand, engage with and follow our tournaments, and also to ensure we have a structure that creates real sporting jeopardy in as many matches as possible.
“We will continue to work with our stakeholders to look at ways in which we can improve both tournaments, an objective which is at the heart of our strategy and commitment to fans, clubs and partners.
“Our competitions truly are the pinnacle of professional club rugby, and we have to ensure that they continue to engage and to enthral existing and new audiences along the way.”
The pool draws will take place in London on June 21, with the opening round of games taking place in December.
Champions Cup qualifiers: Saracens, Sale Sharks, Leicester, Northampton, Harlequins, Exeter, Bath, Bristol, Munster, DHL Stormers, Leinster, Ulster, Glasgow, Vodacom Bulls, Connacht, Cardiff, La Rochelle, Toulouse, Racing 92, Bordeaux-Begles, Lyon, Stade Francais, Toulon, Bayonne.
Challenge Cup qualifiers: Gloucester, Newcastle, Cell C Sharks, Emirates Lions, Benetton, Edinburgh, Ospreys, Scarlets, Dragons, Zebre Parma, Castres, Clermont Auvergne, Montpellier, Pau, Perpignan, Oyonnax, plus two invited teams.
