Paris Saint-Germain and Barcelona opened their UEFA Champions League campaigns with emphatic victories on Wednesday, while Arsenal and Liverpool had to work harder for winning starts and Galatasaray let an early lead slip away in Lisbon.
PSG produced the biggest scoreline of the night with a 6-1 victory over Slovan Bratislava, Barcelona swept aside Feyenoord 5-1, and Stuttgart beat Viking 3-1. Elsewhere, Arsenal edged Napoli 1-0, Liverpool came from behind to defeat Atletico Madrid 2-1, while Sporting recovered from an early own goal to beat Galatasaray 3-1.
Ferran Torres marked Paris Saint-Germain's Champions League opener with a hat-trick as the defending champions brushed aside Slovan Bratislava 6-1 at the Parc des Princes.
Ousmane Dembele scored twice inside the opening 23 minutes before setting up Torres for PSG's third. Torres struck twice more after halftime to complete his hat-trick, while Suleiman Camara pulled one back for Slovan and Fabian Ruiz rounded off the scoring late on.
Torres said PSG had focused on playing with intensity and immediately pressing after losing possession.
"It is impossible, you cannot expect to score a hat-trick," he said.
PSG are seeking a third consecutive Champions League title, a feat achieved only once in the modern competition by Real Madrid between 2016 and 2018.
Barcelona also made a powerful start, beating Feyenoord 5-1 at home.
Raphinha scored twice, while Karim Adeyemi, Lamine Yamal and Gabriel Jesus also found the net. Sem Steijn scored Feyenoord's only goal late in the second half.
Stuttgart produced another convincing home victory as Ermedin Demirovic scored a first-half hat-trick in a 3-1 win over Norwegian side Viking.
Arsenal needed until the 75th minute to overcome Napoli, with captain Martin Odegaard firing in off the post from the edge of the penalty area to secure a 1-0 victory.
Napoli had spent much of the match sitting deep and trying to frustrate last season's runners-up, while Arsenal passed up several opportunities before Odegaard finally broke the deadlock.
The goal came three days after the Norwegian also scored the winner against Chelsea.
Arsenal, who lost last season's Champions League final to PSG on penalties, therefore carried their perfect start to the new campaign into Europe.
Liverpool also came from behind at Anfield, beating Atletico Madrid 2-1 in Andoni Iraola's first Champions League match as a coach.
Marcos Llorente put Atletico ahead after 17 minutes before Dominik Szoboszlai brought Liverpool level shortly before halftime. Alexis Mac Allister then completed the turnaround in the second half.
Iraola praised his players for showing character after the difficult opening and said he had enjoyed his first experience of the competition.
"I've loved it. The atmosphere has been incredible, and I feel lucky, lucky to experience it," he said.
Galatasaray's campaign began with disappointment as the Turkish champions lost 3-1 away to Sporting despite going ahead after only five minutes.
Goncalo Inacio's own goal handed Galatasaray the lead, but Sporting gradually took control and drew level through Geny Catamo in the 27th minute.
Luis Suarez put the Portuguese side ahead from the penalty spot after halftime before Rodrigo Zalazar made it 3-1 with a free kick six minutes later.
The result brought Galatasaray's unbeaten start to the season to an end after three wins and one draw in their opening four domestic matches.
It also continued the club's difficult record in opening Champions League league or group-stage fixtures, with Galatasaray winning only one of their last 10 such matches.
Galatasaray have also now won just once in their last 16 European away matches, with last season's 3-0 victory against Ajax remaining their only success during that run.
New signing Rafael Leao, who came through Sporting's academy before leaving the club following the 2018 attack on players at the training ground, was booed by the home supporters after coming on for Leroy Sane in the 58th minute.
Barcelona 5-1 Feyenoord
Stuttgart 3-1 Viking
Paris Saint-Germain 6-1 Slovan Bratislava
Liverpool 2-1 Atletico Madrid
Sporting 3-1 Galatasaray
Napoli 0-1 Arsenal