Barcelona will face Juventus in the group stage of the Champions League after they were paired together in Group G in the draw, which took place in Geneva on Thursday.
The heavyweight fixture will see Cristiano Ronaldo come up against Barcelona superstar Lionel Messi for the first time since his move to Juventus from Real Madrid in the summer of 2018.
The two men, who have shared 11 of the last 12 Ballon d'Or awards between them, enjoyed a historic rivalry in La Liga, and will resume hostilities in Europe's elite competition next month.
Barca and Juve have been joined in Group G by Dynamo Kiev and Ferencvaros, the Hungarian outfit who beat Celtic en-route to qualifying for the main draw for the first time in their history.
Meanwhile, Manchester United's return to the Champions League has been marked with a draw against last year's Champions League finalists PSG, RB Leipzig and Istanbul Basaksehir in Group H.
Reigning champions Bayern Munich will play Atletico Madrid, Red Bull Salzburg and Lokomotiv Moscow in Group A for a place in the knockout stages, having got their hands on the trophy for the sixth time by beating PSG 1-0 in Lisbon on August 23.
Group D will see 2018 winners Liverpool, who suffered a surprise early exit at the hands of Atletico last term, square off against Ajax, Atalanta and Midtjylland.
13-time winners Real Madrid have been dealt a tough hand in Group B alongside Shakhtar Donetsk, Inter and Borussia Monchengladbach.
Manchester City were handed a more favourable draw against Porto, Olympiacos and Marseille in Group C, as they bid to win the competition for the first time in their history once again.
The last English side to qualify from the Premier League were Chelsea, who will play Europa League winners Sevilla, Krasnodar and Rennes, who will be making their first appearance on Europe's biggest stage, in Group E.
In Group F, Zenit St Petersburg, Borussia Dortmund, Lazio and Club Brugge will do battle, with the 2020-21 edition of the Champions League set to kick off on October 20/21, with fixtures continuing through to early December to decide who will reach the last 16 stage.