The European Rugby Champions and Challenge Cup competitions will return to a multi-pool format for the 2023-24 season.
The Champions Cup will have 24 teams split into four pools of six, with the 18-team Challenge Cup being divided into three pools of six.
In response to the Covid-19 pandemic, each cup had been split into two leagues preceding the knockout stages.
The 2024 finals will take place at Tottenham Hotspur Stadium in May.
The Champions Cup will feature the top eight teams each from the Top 14, Premiership and United Rugby Championship (URC).
The Challenge Cup will be contested by eight URC teams, six Top 14 sides, two Premiership clubs and two yet-to-be-revealed invited clubs.
European Professional Club Rugby (EPCR) says the revised format has been agreed with the help of Premiership Rugby, Ligue Nationale de Rugby and the URC.
The first round of fixtures will begin on Friday, 8 December, six weeks after the final of the 2023 Rugby World Cup.