Manchester City landed the toughest draw in the Champions League group stages as they were drawn against Spanish champions Real Madrid, Dutch giants Ajax and Germany's back-to-back title winners Borussia Dortmund.
Elsewhere, current champions Chelsea face Juventus, Shakhtar Donetsk and Denmark's FC Nordsjaelland. While Scottish side Celtic take on Barcelona as well as Benfica and Spartak Moscow.
There were relatively easy draws for Manchester United and Arsenal as the former picked up Braga, Galatasaray and Cluj; the latter Schalke, Olympiakos and Montpellier.
Real Madrid midfielder Cristiano Ronaldo admitted that Group D was the toughest and said: "It is the most difficult group in my opinion and I think that's the same for most people. But we are champions of Spain and we are ready to compete with everybody.''
Dortmund boss Jurgen Klopp told Sky: "You should have played against Real Madrid at least once in your life. We will fight against world-class players, I am looking forward to it."
The German club's chairman Hans-Joachim Watzke: "This is an incredible tough but also incredible attractive group with three former Champions League winners and the English champion. All four teams have won their league. In such a group heroes are born. We want to make it out of the group!"
City skipper Vincent Kompany said his team-mates should be philosophical about the draw.
"Looks like we're not going to get any easy games again this year but it is certainly a good group for the fans,'' he tweeted. "I'm looking forward already!''