Real Madrid begin their Champions League defence against Roma, while Barcelona are drawn Tottenham Hotspur and Valencia get two giants.
Madrid have won the last three Champions League titles, and waiting for them in Group G are Roma - who beat Barca in the quarter-finals last season - as well as CSKA Moscow and Viktoria Plzen.
As for Barca, they are joined in Group B by Tottenham - who overcame Los Blancos in the 2017-18 group stage - PSV and Inter, the Catalans' slayers in the 09-10 semi-finals.
Atleti, meanwhile, are rewarded for winning the Europa League last term with a Group A that includes Borussia Dortmund, Monaco and Belgian side Club Brugge.
Finally, Valencia's return to the big time involves an uphill task to qualify for the knockout stages, Los Che being paired with Juventus and Manchester United in Group H.
The group will also see former Madrid star Cristiano Ronaldo return to Old Trafford as a Juve player for the first time.
Group A: Atletico Madrid, Borussia Dortmund, Monaco, Club Brugge
Group B: Barcelona, Tottenham Hotspur, PSV, Inter
Group C: Paris Saint-Germain, Napoli, Liverpool, Red Star Belgrade
Group D: Lokomotiv Moscow, Porto, Schalke, Galatasaray
Group E: Bayern Munich, Benfica, Ajax, AEK Athens
Group F: Manchester City, Shakhtar Donetsk, Lyon, Hoffenheim
Group G: Real Madrid, Roma, CSKA Moscow, Viktoria Plzen
Group H: Juventus, Manchester United, Valencia, Young Boys