Cristiano Ronaldo scored 118 goals in 292 appearances for United.
The draw for the group stage took place on Thursday, with United being drawn in Group H alongside Valencia, Young Boys, and the Italian side.
Following their second place finish last season, Jose Mourinho's side were seeded in pot two alongside Tottenham Hotspur, who were drawn in a group with Barcelona.
Liverpool, who were seeded in pot three, have been drawn in the group of death alongside Napoli and Paris Saint-Germain, while Manchester City's seeding in pot one has allowed them to avoid any real danger, bar perhaps Shakhtar Donetsk.
It is a tough draw for United, as Valencia are a strong side returning to the competition after a two-year absence but Mourinho's side should be optimistic that they have the quality to progress.
It has been a turbulent few weeks for the club, with rumours circling about the manager's future following a string of poor results, but the prospect of Ronaldo's return to Old Trafford may brighten the spirits of some United fans.
The 33-year-old has played at the Theatre of Dreams just once since he left the club in 2009, he received a loving reception from the United fans that night and should expect an equally warm atmosphere on this occasion.
United's clashes with the Bianconeri will be a huge occasion for Paul Pogba as well, who spent four years in Turin between his two spells in Manchester.
Some Red Devils' fans took to Twitter to express their excitement, and a little bit of fear, about the draw in general and the return of Ronaldo.
United drawn against Juventus. Cristiano Ronaldo returns home, Paul Pogba takes on his old club, too... Some tie, that... #mufc— OldTraffordFaithful (@OTFaithful) August 30, 2018
United in the same group as Juve. Ronaldo is coming back to Old Trafford next season. You can’t write this stuff man.— Ryan. (@Vintage_Utd) August 30, 2018
Ronaldo’s coming home!— Devil in D’s Tales (@DarynDecruz) August 30, 2018
Gonna be a fun ride whatever happens, always happy to face Ronnie.— CT (@MclarenCT) August 30, 2018
It will be memorable both in Manchester and Turin. Both players will get a great reception. It will be 2 titanic games to look forward to as well. Hope Mourinho can galvanize the team with enough belief to achieve positive results. Looking forward to it. ⚽️— Rashid Uzzaman (@rashiduzzaman82) August 30, 2018
Exciting! We play better against bigger sides anyway (usually). Ronaldo’s return will be special, Pogba and Mata also playing against former teams. Hope we get some good games to watch. Glad we’re getting to play some different teams that we haven’t played in a while too!— Laura Salmond (@G_O_T_W) August 30, 2018
Manchester United's record v Juventus:— Lloyd Neinner (@NeinnerLloyd) August 30, 2018
- Five wins
- Five losses
- Two draws
Pogba, Ronaldo, Mourinho v Allegri.
Going to be brilliant!