Manchester United got their Champions League campaign underway in emphatic style as Marcus Rashford's late goal earned them a 2-1 victory at Paris St-Germain.
The defeat was the French champions first loss at home in the group-stages in 16 years.
Rashford netted three minutes from time, 18 months after scoring the decisive goal in a 3-1 win at PSG that sent United into the quarter-finals, after a 2-0 first-leg home defeat.
Ole Gunnar Solskjaer's United side went ahead in the Group H encounter with a twice-taken Bruno Fernandes first-half penalty, before Anthony Martial's own goal after the break gifted PSG the equaliser, only for Rashford to wrap up the win with a precise low shot.
Thomas Tuchel's side looked nothing like the one who reached the final of last season's competition, as they lacked energy throughout in an empty Parc des Princes.
Paul Pogba surprisingly started on the United bench, while Marquinhos was not included in PSG's starting 11, having not recovered in time from a groin injury he sustained on Brazil duty.
He was replaced by Abdou Diallo, who fouled Anthony Martial in the box, handing the visitors a penalty which was converted by Fernandes on his second attempt.
Keylor Navas had saved the first spot kick, but it had to be retaken after the keeper was judged to have moved off his goal line.
It was a poor start from PSG, who had two chances through Angel Di Maria and Layvin Kurzawa, but lacked aggression.
Fernandes went close to doubling United's tally six minutes before the break with a thumping right-footed effort that Navas just tipped around the post.
Kylian Mbappe slalomed through the defence before curling a shot towards the top-right corner, but United keeper David de Gea stretched to tip the ball away three minutes into the second half.
Seven minutes later, Martial headed a Neymar corner into his own net, handing PSG an unexpected equaliser.
The home side, who were also without the injured Mauro Icardi and Marco Verratti, started to find spaces in the defence of Ole Gunnar Solskjaer's side, but they could not capitalise.
The visitors pressed harder in the closing stages and deservedly regained the advantage when Rashford beat Navas with a low, diagonal shot into the bottom corner from just inside the box.
United next host RB Leipzig, who beat Basaksehir 2-0, while PSG will travel to Istanbul to face the Turkish side.
Elsewhere, Chelsea played out a goalless draw against Sevilla, Lazio beat Borussia Dortmund 3-1 and Juventus beat Dynamo Kyiv 2-0.
