BT Sport has secured exclusive rights to broadcast all the matches of the European Rugby Champions Cup and the European Rugby Challenge Cup, in what is a major blow to rival Sky Sports.
The broadcaster did not disclose any financial details of the new deal, which will kick off from the beginning of the 2018-19 season and run at least until the end of the 2021-22 campaign.
Under the new agreement, up to 134 matches across both competitions over nine weekends will be broadcast live on BT Sport.
"BT Sport is now the home of elite European rugby, as well as the home of Aviva Premiership Rugby," said Andy Haworth, BT's managing director of content and strategy.
"We're proud to have won all of the live rights for this fantastic competition. We're extremely passionate about our rugby coverage and will continue to work hard to grow the profile of the sport."
Sky Sports had exclusively broadcast the Champions Cup - or Heineken Cup, as it was known until 2014 - from its inception in 1995 until the 2014-15 season, when the European Professional Club Rugby (EPCR) - European rugby's governing body - split the coverage between Sky and BT in order to increase revenues.
Broadcasting rights for the Challenge Cup, European rugby's second tier competition, were also split in 2015, after Sky had held them exclusively since 1996.
Vincent Gaillard, the chief executive of EPCR, added: "We are delighted to move to a single pay-TV platform for European club rugby with a premium broadcaster in BT Sport, who share our commitment to the promotion of our competitions.
"We look forward to further developing that relationship to continually create outstanding rugby experiences for fans across the United Kingdom and Ireland."
Since launching in 2013, BT Sports has secured the exclusive rights to the Aviva Premiership Rugby and has broadcast live at least 37 games in both European elite competitions per season since the 2014-15 campaign.
Sky, meanwhile, retains the rights to the Guinness Pro 12, France's Top 14 as well Super Rugby, which includes teams from Argentina, Australia, Japan, New Zealand and South Africa.
The broadcaster has also exclusive rights to the British and Irish Lions tour, international winter and summer Tests - with the exception of the Six Nations - and the Rugby Championship.
Last week, Sky beat off BT to retain the bulk of TV rights for domestic and international cricket, as part of a new-five year deal worth £1.1bn ($1.4bn) to the England Cricket Board (ECB).
The agreement, which dwarfs Sky's current £75m contract, will run between 2020 and 2024 and will see the the TV giant exclusively broadcast England's international matches across all formats of the game at home and abroad.