Arsenal were handed a tough draw in the Champions League group stages as they were paired with Bayern Munich.
The Gunners were knocked out of the tournament by the German giants in successive seasons in 2013 and 2014 and their presence in Group F represents a major challenge for the north London club, who have started the Premier League season with four points from three games.
Bayern were beaten by Barcelona in the Champions League semi-finals last season but went on to complete a first ever domestic double and have reinforced their squad over the summer with the acquisitions of Juventus midfielder Arturo Vidal and Shakhtar forward Douglas Costa.
Arsene Wenger’s side, who were beaten at home by West Ham on the opening day of the season, also face Olympiakos and Dinamo Zagreb.
Manchester City were handed a similarly tough draw and will play last season’s beaten finalists Juventus, Europa League champions Sevilla and Borussia Monchengladbach.
Jose Mourinho will return to Porto with Chelsea and the reigning Premier League champions will also play Dynamo Kiev and Maccabi Tel-Aviv in Group G.
Mourinho was in charge at Porto from 2002 to 2004 and won both the UEFA Cup and the Champions League during that time.
After a one-year absence, Manchester United will resume Champions League competition against PSV Eindhoven – meaning an early return to Holland for winger Memphis – CSKA Moscow and Wolfsburg.
Current holders Barcelona drew Bayer Leverkusen, Roma and BATE Borisov.
The ceremony to draw the groups also included the presentation of the UEFA Best Player award, which was given to Barcelona’s Lionel Messi.
Full Champions League group stage draw:
Group A: PSG, Real Madrid, Shakhtar Donetsk, Malmo.
Group B: PSV Eindhoven, Manchester United, CSKA Moscow, Wolfsburg.
Group C: Benfica, Atletico Madrid, Galatasaray, Astana.
Group D: Juventus, Manchester City, Sevilla, Borussia Monchengladbach.
Group E: Barcelona, Bayer Leverkusen, Roma, BATE Borisov.
Group F: Bayern Munich, Arsenal, Olympiakos, Dinamo Zagreb.
Group G: Chelsea, Porto, Dynamo Kiev, Maccabi Tel-Aviv.
Group H: Zenit, Valencia, Lyon, KAA Gent.