A comprehensive wrap of all the collated fixtures, scores and match reports from the UEFA Champions League:
TUESDAY, 14 SEPTEMBER
Sevilla 1-1 RB Salzburg
Young Boys 2-1 Man United - FULL MATCH REPORT
Cristiano Ronaldo scored 13 minutes into his Champions League return for Manchester United but Ole Gunnar Solskjaer's 10-man side crashed to a 2-1 defeat at Young Boys of Switzerland on Tuesday.
Ronaldo turned in from a Bruno Fernandes cross to give United the lead in Bern but Aaron Wan-Bissaka was sent off on 35 minutes for a foul on Christopher Martins Pereira.
Swiss champions Young Boys equalised through Nicolas Moumi Ngamaleu midway through the second half before Jordan Siebatcheu hit a 95th-minute winner after Jesse Lingard's ill-advised backpass.
Lille 0-0 Wolfsburg
Villarreal 2-2 Atalanta
Chelsea 1-0 Zenit - REACTION
Romelu Lukaku broke the deadlock for Chelsea after 69 minutes at Stamford Bridge to earn the holders a one-goal victory over Zenit, whose Krestovsky Stadium in Saint Petersburg is the venue for next May's final.
Lukaku headed in Cesar Azpilicueta's cross to give Thomas Tuchel's team a winning start in Group H.
Malmo 0-3 Juventus
Barcelona 0-3 Bayern Munich
Bayern Munich gave Barcelona a brutal demonstration of how far their opponents have fallen by strolling to victory in the Champions League on Tuesday, with Robert Lewandowski scoring twice in a rout at Camp Nou.
Without Lionel Messi for a first European campaign since 2003, Barca were outplayed by Bayern, who might have scored more but in the end settled for three thanks to Thomas Mueller's deflected opener and Lewandowski's double.
When Lewandowski made it two before the hour, the possibility of another humiliation in the mould of last year's 8-2 defeat by the same opponents in Lisbon felt very real.
Instead, Bayern delivered perhaps an even louder message about the gulf in class by easing off in the latter stages, as Barca's fans expressed their anger, dismay and finally a sense of resignation.
Dynamo Kyiv 0-0 Benfica
WEDNESDAY, 15 SEPTEMBER
Besiktas 1-2 Dortmund
England midfielder Jude Bellingham shone with a goal and an assist for Erling Braut Haaland as Borussia Dortmund kicked off their Champions League campaign with a 2-1 win at Besiktas.
Bellingham silenced the boisterous crowd in Istanbul with the opening goal and then unpicked the home defence to serve up a simple tap-in for Haaland to claim his 21st Champions League goal just before half-time.
Javi Montero headed in a consolation goal for Besiktas deep in added time.
Sheriff 2-0 Shaktar Donetsk
Inter Milan 0-1 Real Madrid
Rodrygo sank wasteful Inter Milan with the last-gasp winner at the San Siro which gives Real Madrid the perfect start to their Champions League campaign.
Italian champions Inter are trying to make the competition's knockout rounds for the first time since 2011/12 but they were punished for letting a series of opportunities slip by before Brazilian Rodrygo's beautifully struck goal in the final minute of the Group D clash.
It was a harsh result for Inter against Carlo Ancelotti's Madrid, who up to that point had shown little of the attacking verve which has brought them 13 goals in four La Liga games so far this season
Atletico Madrid 0-0 Porto
Club Brugge 1-1 PSG - REPORT
Messi lined up with both Neymar and Kylian Mbappe for the first time, after being limited to just 24 minutes in a PSG shirt since his shock exit from Barcelona.
Ander Herrera, who scored twice in the weekend win over Clermont, gave PSG the lead by steering in Mbappe's cross on 15 minutes, but Brugge soon levelled through Hans Vanaken.
Messi curled against the bar from the corner of the area but PSG then lost Mbappe to injury and had to settle for a point against a team viewed as makeweights in a demanding Group A.
Liverpool 3-2 AC Milan - REPORT
Liverpool captain Jordan Henderson hit the winner for Jurgen Klopp's side as they came from behind to defeat Milan at Anfield in a meeting of two clubs who have combined for 13 European Cups.
Fikayo Tomori inadvertently deflected in Trent Alexander-Arnold's effort to put Liverpool in front but Mohamed Salah saw his penalty saved by Milan goalkeeper Mike Maignan.
The momentum swung sharply in Milan's favour as Ante Rebic and Brahim Diaz struck twice in as many minutes before the break.
Salah atoned with an equaliser on 49 minutes that was initially discounted for offside before Henderson drove in on the half-volley from the edge of the box.
Man City 6-3 RB Leipzig - REPORT
Pep Guardiola's City, beaten 1-0 by Chelsea in May's final in Porto, overcame a hat-trick from Christopher Nkunku to beat RB Leipzig at the Etihad Stadium.
Nathan Ake headed City ahead from a corner and Nordi Mukiele's own goal doubled their advantage, but Nkunku nodded in to get Leipzig back in the game.
Riyad Mahrez added a third with a penalty before half-time only for Nkunku to head in again early in the second period.
Jack Grealish notched his first Champions League goal following his British record £100 million ($136 million) signing, with Nkunku completing his treble before Joao Cancelo and Gabriel Jesus strikes wrapped up a wild victory for City.
Sporting 1-5 Ajax