
Record 15-time champions Real Madrid defeated Inter Milan 2-1 at the Santiago Bernabeu, while Manchester City, the 2023 champions, secured a 2-0 victory over Porto.
Both clubs are expected to challenge defending champions Paris Saint-Germain this season, with Mbappe and Haaland likely to play key roles in their title bids.
Mbappe opened the scoring after 14 minutes, taking his Champions League tally to 71 goals and moving level with Real Madrid legend Raul in fifth place on the competition's all-time scoring list.
Haaland, meanwhile, scored twice against Porto to take his Champions League total to 59 goals in 59 appearances.
Borussia Dortmund edged Villarreal 3-2, while Real Betis defeated Lille by the same score. Aston Villa also won 3-2 against Club Brugge, and AEK Athens beat LASK 1-0.
Defending champion PSG will begin its title defense on Wednesday against Slovan Bratislava.
Mourinho makes winning return
Jose Mourinho marked his return to Champions League management with a victory as Real Madrid coach, despite Inter enjoying 61% possession.
Madrid took advantage of two costly first-half mistakes by the Italian side.
Inter lost possession deep in its own half, allowing Brahim Diaz to set up Mbappe, who fired a low shot past goalkeeper Josep Martinez.
Martinez was again caught out when Federico Valverde pressured him inside the penalty area and poked the ball into an unguarded net.
Inter reduced the deficit through Carlos Augusto in the 77th minute, setting up a tense closing period.
“There’s so much criticism when a game is boring, but today it was crazy — it could easily have ended 7-6,” Mourinho said.
Mourinho won the Champions League with Inter in 2010 and is seeking a third title as a coach.
Haaland continues scoring form
Haaland maintained his impressive scoring run against Porto, having scored five goals in his previous three matches.
The Norwegian striker finally broke the deadlock two minutes after halftime, heading the ball into the net. He added a second in stoppage time with a side-footed finish to secure City's victory.
The result also maintained new coach Enzo Maresca's perfect start.
“We have to learn. Enzo demands a lot from us and we have to demand a lot from each other,” Haaland said. “We have to win games because at Man City, you have to win trophies.”
Villa end poor start
Aston Villa put their difficult start to the domestic season behind them with a 3-2 victory over Club Brugge in Belgium.
John McGinn scored the opening goal of the Champions League campaign in the 11th minute with a low angled effort.
Brugge equalized through Hugo Vetlesen, but Emiliano Buendia and Nicolas Jackson scored before halftime to give Villa a 3-1 lead.
Nicolo Tresoldi pulled one back from the penalty spot in the 61st minute, but Villa held on.
The victory ended Villa's winless and goalless start to the 2026-27 season following defeats by Brighton and Arsenal and a goalless draw with newly promoted Hull.
Dortmund teenager hospitalized
Dortmund teenager Konstantinos Karetsas was taken to hospital after collapsing during his Champions League debut against Villarreal.
The German club said the 25-year-old? [Need correction: Karetsas is a teenager] — teenager had to leave the field because of circulatory problems and was sent to hospital for further tests.
Serhou Guirassy scored twice for Dortmund and also put the ball into his own net as the German side secured a dramatic victory.
Guirassy put Dortmund ahead 2-1 in the 80th minute and converted a penalty five minutes later. Villarreal pulled another goal back through an added-time own goal.
Parrott scores again for Betis
Ireland international Troy Parrott continued his impressive start at Real Betis by scoring the winner in their 3-2 victory over Lille.
Parrott had also scored a late winner against Real Madrid in La Liga on Friday, making his latest goal another decisive contribution for his new club.
AEK Athens secured their win over LASK through Razvan Marin's superb first-half free kick, reports UNB.