This is what we found on Wikipedia regarding the European Rugby Champions Cup:

The European Rugby Champions Cup (known as the Investec Champions Cup for sponsorship reasons) is an annual rugby union tournament organised by European Professional Club Rugby (EPCR). It is the top-tier competition for clubs who compete in a predominantly European league. Clubs qualify for the Champions Cup via their final positions in their respective national/regional leagues (English Premiership, French Top 14, and United Rugby Championship) or via winning the second-tier Challenge Cup; those that do not qualify are instead eligible to compete in the second-tier Challenge Cup.

Between 1995 and 2014, the equivalent competition was known as the Heineken Cup and was run by European Rugby Cup. Following disagreements between its shareholders over the structure and governance of the competition, it was taken over by EPCR and its name was changed to the European Rugby Champions Cup, without title sponsorship. Heineken returned as sponsor for the 2018–19 season, resulting in the competition being known as the Heineken Champions Cup. Although they are technically two separate competitions, run by different organisations, the European Rugby Cup and the European Rugby Champions Cup are recognised as one title chain of elite club championships in Europe, with teams that have won multiple titles ranked, for example, by the aggregate of their wins in both versions.

French clubs have the highest number of victories (12 wins), followed by England (10 wins) and Ireland (7 wins). England has the largest number of winning teams, with six clubs having won the title. The competition has been won by thirteen different clubs, eight of which have won it more than once, and five successfully defended their title including a unique three-in-a-row made by Toulon between 2012–13 and 2014–15. Toulouse is the most successful club in the tournament's history, having won it 6 times, including the first season of the tournament in the 1995–96 season. Toulouse are the current European champions, having beaten Leinster 22–31 in the 2024 final in London, England. Toulouse completed "the Double" (Heineken Cup/European Rugby Champions Cup-National Championship) 3 times (1995-1996, 2020-2021 and 2023-2024), a record in Europe.