Manchester City 6-3 RB Leipzig
Last season's finalists started their group stage phase with a thrilling 6-3 win over RB Leipzig.
The Citizens were quite rampant in the first half after netting three goals through Nathan Ake, Riyad Mahrez and a Nordi Mukiele own goal.
Christopher Nkunku had a night to remember after bagging a hat-trick for Leipzig, but City went onto score three more in the second half via Jack Grealish, Joao Cancelo and Gabriel Jesus.
Liverpool 3-2 Milan
Liverpool got off to a positive start defeating AC Milan in a five-goal thriller at Anfield.
The Reds took the lead on nine minutes with Fikayo Tomori deflecting Trent Alexander-Arnold's cross into his own net, before Mohamed Salah squandered a chance to double the lead on 14 minutes after seeing his penalty saved by Maigan.
Milan brought themselves level in the 42nd minute through neat finish from Ante Rebic and they were ahead two minutes later thanks to Brahim Diaz's finish.
Salah brought the Reds level shortly after the break, before Jordan Henderson secured the winning goal with an impressive strike in the 69th minute.
Atletico Madrid 0-0 Porto
Atletico Madrid and FC Porto could not be separated in the Spanish capital after playing to a goalless draw on Wednesday evening.
The visitors did end the game with 10 men though as Chancel Mbemba picked up his second yellow card in second-half stoppage time.
Beskitas 1-2 Borussia Dortmund
Borussia Dortmund made a winning start to their UEFA Champions League campaign after defeating Besiktas 2-1 on Wednesday evening.
England Jude Bellingham opened the scoring for the visitors on 20 minutes with a neat volley from a tight angle after being played in by Thomas Meunier.
The second goal arrived on the stroke of halftime when Bellingham turned provider to pick out Erling Haaland, who opened his account for the tournament.
The hosts did set up a nervy finish after pulling a goal back in the 94th minute, but it was too little too late as the visitors took the spoils.
Sporting Lisbon 1-5 Ajax Amsterdam
Ajax Amsterdam showed Sporting Lisbon no mercy after romping to a 5-1 victory at Estadio Jose Alvalade.
A brace from Sebastian Haller and a solitary strike from Steven Berghuis had the visitors 3-1 ahead after Paulinho had netted for Sporting.
The night belonged to Haller who bagged two more goals in the second to take his tally to four on the night.
Sheriff 2-0 Shakhtar Donetsk
Sheriff Tiraspol marked their Champions League debut with maxium points after defeating Shakhtar Donetsk 2-0 in Tiraspol.
Sheriff qualified for the tournament for the first time in their history via the play-offs.
Adama Taore opened the scoring with the club's first-ever goal in the tournament on 16 minutes before Momo Yansane doubled the lead in the 62nd minute.
Click through the gallery below to see the highest-paid players in the Champions League this season: