As well as a rematch of the spectacular Roma-Liverpool semi-final.
Thursday's Group Stage draw saw Barca join Tottenham, PSV and Inter in Group B while reigning champions Madrid meet Roma, CSKA and Viktoria Plzen in Group G. Red Star won the old European Cup in 1991, one year before the format changed.
Inter Milan, back in the competition after a six-season absence, were pitted against Barcelona and Tottenham Hotspur.
How the Champions League's dominant club and defending champions perform in the competition following the sale of its greatest goalscorer in Cristiano Ronaldo remains the campaign's biggest question, its dominant topic.
Recall that the miners were once in the group stage thanks to a victory in the championship 2017/18.
He will come up against his compatriot Jose Mourinho, under whom he played during his time at Real, while United midfielder Paul Pogba can also look forward to facing his old team.
The LaLiga teams have dominated the competition in recent seasons with Madrid winning four and Barca one of the last five.
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United were grouped alongside Juventus , Valencia and Young Boys for a somewhat tricky Champions League group stage. Ronaldo's agent, Jorge Mendes , also branded the decision to give the award to Modric as "shameful".
October 2 shapes as a huge day for United, who must strike first when they host Los Che on Matchday 2. While Mohamed Salah, who had a breathtaking run in the Champions League had to remain empty-handed.
The three smug gentleman, led by club president Mustafa Cengiz, sat smiling and nodding, even exchanging a celebratory handshake, as they congratulated themselves on ending up in the "weaker" group.
The German boss believes Liverpool's Brazilian trio of Alisson, Roberto Firmino and Fabinho will particularly enjoy facing PSG as they battle against global team mate Neymar.
Valencia and outsiders Young Boys, Swiss champion for the first time in 32 years, are also in Group H with United and Juventus.
"I hope that they make it to the second round but it's not going to be easy for them".
Inter's wildly unpredictable form under Luciano Spalletti means anything can happen in Group B where they face Barcelona, PSV Eindhoven and Tottenham.
"Real Madrid, due to their history and tradition, and that they have won four of the last five titles, including three in a row".