Video Assistant Referees (VAR) will be used from the last 16 of this season's Champions League, UEFA has confirmed.
European football's governing body had already committed to using VAR in its competitions from 2019-20 onwards.
But last month, UEFA president Aleksander Ceferin and European Club Association chairman Andrea Agnelli revealed there was scope to bring it in earlier.
This move was confirmed at the Nations League Finals draw in Dublin on Monday, with all forthcoming knockout matches in UEFA's flagship club competition to benefit from VAR.
Alongside the Champions League rollout, VAR will also be used in this season's Europa League final – but not, it seems, in the knockout rounds – as well as the Nations League Finals 2019 and next year's European Under-21 Championship.
"We are ready to use VAR earlier than initially planned and we are convinced that it will be beneficial for our competitions as it will provide valuable help to match officials and will allow to reduce incorrect decisions," Ceferin said.
VAR featured at the 2018 World Cup following a trial at FIFA competitions, including the 2017 Confederations Cup, and is increasingly present across football's major domestic leagues.
The Premier League will introduce VAR alongside its Goal Decision System from 2019-20.