UEFA has confirmed that video assistant referees (VAR) will be used in the Champions League from next season.
VAR will also be brought into the Europa League, though a year later from 2020-21, as well as the 2019 UEFA Super Cup, Euro 2020 and the UEFA Nations League finals in 2021.
European football's governing body had resisted implementation of the VAR system, which allows key incidents to be reviewed with the use of video replays and was used at the World Cup in Russia this year.
"We are confident that introducing Video Assistant Referees in August 2019 will give us enough time to put in place a robust system and to train match officials to ensure an efficient and successful implementation of VAR in the UEFA Champions League, the world's flagship club competition," UEFA president Aleksander Ceferin said in a statement.
Ceferin said last month that VAR would be introduced from the playoff round onwards, but will not be used in any European competition this season.
VAR is currently used in most of Europe's top leagues, including La Liga, Serie A, the Bundesliga, Ligue 1 and Portugal's Primeira Liga.
The English Premier League, like UEFA, has resisted in favour of further testing but is expected to approve its use from next season.