Wayne Rooney scored twice and made another as David Moyes' first Champions League match in charge of Manchester United ended in a 4-2 win against Bayer Leverkusen.
Manuel Pellegrini also got off to a winning start as three goals in the second half handed Manchester City a 3-0 triumph at Viktoria Plzen, with Edin Dzeko, Yaya Toure and Sergio Aguero on target.
Holders Bayern Munich cruised to a 3-0 victory over CSKA Moscow under Pep Guardiola, while Cristiano Ronaldo netted a hat-trick in a 6-1 victory for Real Madrid at Galatasaray, as Juventus were held to a 1-1 draw at FC Copenhagen.
Rooney joined Manchester United's exclusive 200 club, scoring twice as the Red Devils opened their Champions League campaign with an encouraging 4-2 win over Bayer Leverkusen.
The forward put United ahead midway through the first half with a first-time effort from Patrice Evra's cross, although Bayer Leverkusen argued with some justification that an offside Antonio Valencia had impeded keeper Bernd Leno.
Still, it did not look like being a particularly memorable night for the England forward when an inexplicable failure to either tap into an empty net or provide an opportunity for Robin van Persie to do so after he had skipped round Leno was followed within a minute by Simon Rolfes' equaliser.
However, Van Persie soon restored United's advantage before Rooney entered the history books as he seized on the loose ball after Emir Spahic had got his head to David de Gea's long punt downfield and finished with ease.
It was a landmark effort that meant Rooney emulated Sir Bobby Charlton, Denis Law and Jack Rowley in reach 200 United goals.
More importantly in the short-term, it launched David Moyes' Champions League career in the perfect style as Rooney provided a late fourth for Valencia.
Manchester City struck three times in the space of ten second half minutes to get their latest Champions League campaign off to a 3-0 winning start against Viktoria Plzen.
City were frustrated by the Czech champions in the first half at the compact Doosan Arena but burst into life after the break with goals from Edin Dzeko, Yaya Toure and Sergio Aguero.
The lively Aguero had also hit the post in the first half while Matus Kozacik also made good early saves from Dzeko and Jesus Navas in the Group D encounter.
The result was the perfect start in the competition for City's new manager Manuel Pellegrini and lifted spirits after a mixed start to the campaign ahead of Sunday's derby against Manchester United.
Bayern Munich began the defence of their Champions League title against CSKA Moscow with a 3-0 victory at the Allianz Arena.
David Alaba, Mario Mandzukic and Arjen Robben were on target for Bayern, who have now won their last ten opening Champions League fixtures.
Real Madrid ran riot in the second half against Galatasaray to make a major statement about their ambitions in the Champions League as they triumphed 6-1.
Although Galatasaray started strongly, they crumbled after Isco made the breakthrough late in the first half as Cristiano Ronaldo, with a hat-trick, and Karim Benzema feasted on some poor defending.
Gareth Bale started the match on the bench, but came on midway through the second half and created one of Ronaldo's goals.
There was a late consolation for the hosts from Umut Bulut, but it was not enough to bring even a flicker of emotion to the face of disconsolate coach Fatih Terem, who started the night full of hope but ended it with his team in tatters.
Juventus were frustrated by an inspired performance from FC Copenhagen goalkeeper Johan Wiland as they were held to a 1-1 draw in their Champions League opener in Denmark.
The visitors missed an almost endless succession of chances, especially after the break, as they began their Group B campaign slowly.
At half-time it looked like it could have been worse, with the Danes leading from Nicolai Jorgensen's 13th-minute goal.
But Fabio Quagliarella levelled nine minutes into the second half.
He also headed against the bar as the Italians created enough chances to win several games, only to see them go begging, thanks to a series of splendid saves by Wiland.
Paris Saint-Germain scored three and missed a penalty in a one-sided second half as they got their Champions League campaign off to a flying start with a 4-1 win at Olympiakos.
A potentially tricky opener to Group C turned out to be anything but as the visitors ran riot after the break, two Thiago Motta headers in quick succession taking the score from 1-1 to 3-1.
Marquinhos headed a fourth late on, minutes after Zlatan Ibrahimovic had had a penalty saved by Roberto Jimenez, without whom the Greeks would have been facing up to a much heavier defeat.
The hosts had been very much in the contest at the break, Vladimir Weiss having cancelled out Edinson Cavani's opener for the visitors, but they were simply blown away in the second period.
The win sent PSG top of the group, level on points with Benfica, who enjoyed a 2-0 home win over Anderlecht.
Filip Djuricic and Luisao were on target as Benfica claimed a 2-0 victory from their Champions League Group C opener against Anderlecht.
Alex Teixeira served Real Sociedad a harsh lesson about life in the UEFA Champions League as the Brazilian's two goals gave Shakhtar Donetsk a 2-0 win in their Group A opener at the Estadio Municipal de Anoeta.
Information from the Press Association was used in this report.