Lionel Messi and Neymar may no longer be team-mates but both wasted no time in getting on the scoresheet as Barcelona, Paris, Bayern, Manchester United and Chelsea were among the opening winners.
Group A
Manchester United 3-0 Basel
Basel had their chances early on and Paul Pogba went off injured but his replacement Maroune Fellaini headed in an Ashley Young cross and Romelu Lukaku continued his rich vein of form for his new club to turn home a Daley Blind ball. Another substitute, Marcus Rashford, got the third.
Benfica 1-2 CSKA Moskva
CSKA secured their first group away win since November 2014 as they recovered from falling behind to a 50th-minute Haris Seferović goal. Vitinho equalised from the penalty spot and substitute Timur Zhamaletdinov won it with 19 minutes left.
Group B
Bayern München 3-0 Anderlecht
Bayern never looked back after Sven Kums was sent off in the 11th minute for a foul on Robert Lewandowski, who swiftly converted the resulting penalty. Thiago Alcántara doubled Bayern’s advantage in the second half and Joshua Kimmich added a late third.
Celtic 0-5 Paris Saint-Germain
All of Paris’s front three helped themselves to first-half goals in Glasgow, where Neymar and Kylian Mbappé both struck for their new club before Edinson Cavani converted a 40th-minute penalty. Mikael Lustig netted a late own goal and Cavani’s flicked diving header made it five.
Group C
Chelsea 6-0 Qarabağ
Chelsea never looked back after Pedro Rodríguez’s fifth-minute opener as Qarabağ suffered a heavy defeat on a night when they became the first Azerbaijani club to play in the group stage.
Roma 0-0 Atlético Madrid
The visitors had most of the possession but Allison Becker in the Roma goal ensured the points were shared.
Group D
Barcelona 3-0 Juventus
Lionel Messi moved on to 99 UEFA club competition goals either side of an Ivan Rakitić effort as Barcelona exacted a little bit of revenge for their quarter-final elimination by Juventus last season.
Olympiacos 2-3 Sporting CP
Sporting will welcome Barcelona in high spirits in a fortnight after a fine win in Greece. Seydou Doumbia, Gelson Martins and Bruno Fernandes put the visitors three up at half-time and they protected the points despite substitute Felipe Pardo pulling one back in the 89th minute and scoring again in added time.