Jose Mourinho's side were drawn from pot two to face the Serie A champions, who signed former Red Devils and Real Madrid star Ronaldo this summer. The Italian and English giants will compete with third seed Valencia and then Swiss side Young Boys.
Ronaldo won four Champions League crowns in his nine-year spell in Spain since then and Juve are hoping last season's top scorer can continue dominate the continent after arriving in Turin.
But the Italian side will have to unseat Real Madrid from the throne they have held for the past three years first.
The reigning champions may be without their star player or coach from last year, but they will be aiming to go all the way once again. Julen Lopetegui's men begin their defence in Group G, where they will face Roma, CSKA Moscow and Viktoria Plzen.
Group B looks to be particularly tough, as Barcelona take on Tottenham, PSV and Inter, while last year's finalists Liverpool have no easy task in taking on Paris Saint-Germain, Napoli and Red Star Belgrade.
Meanwhile, Premier League champions Manchester City are in Group F with Shakhtar, Lyon and Hoffenheim and in Group A, Europa League winners Atletico Madrid will take on Borussia Dortmund, Monaco and Club Brugge.
German giants Bayern Munich are with Benfica, Ajax and AEK Athens in Group E, and Lokomotiv Moscow were the first seed for Group D and will take on Porto, Schalke and Galatasaray.
Champions League 2018-19 groups
|Group A||Group B||Group C||Group D|
|Atletico Madrid||Barcelona||PSG||Lokomotiv Moscow|
|Club Brugge||Inter||Red Star Belgrade||Galatasaray|
|Group E||Group F||Group G||Group H|
|Bayern Munich||Man City||Real Madrid||Juventus|
|Benfica||Shakhtar Donetsk||Roma||Manchester United|
|AEK Athens||Hoffenheim||Viktoria Plzen||Young Boys|