Ideye Brown struck the decisive goal for Olympiakos at the Maksimir Stadium to send Dinamo Zagreb spinning to a second Group F Champions League defeat.
Stefan Mitrovic's own goal allowed Valencia to take a big step towards qualification from Champions League Group H as Gent were beaten 2-1 at the Mestalla.
Juan Mata was the star of the show as Manchester United got off the mark in the Champions League with a narrow 2-1 win over Wolfsburg.
Cristiano Ronaldo's double took him past 500 career goals and handed Real Madrid a narrow 2-0 Champions League victory over 10-man Malmo.
Sergio Aguero struck a last-gasp penalty winner as Manchester City came from behind to ignite their Champions League campaign with a 2-1 win at Borussia Monchengladbach.
Juventus may be struggling in Serie A but it is a different story in the Champions League with the Italian giants clinching the second win in as many games on Wednesday with a home triumph over Sevilla.
Zlatan Ibrahimovic was frustrated in his attempts to overhaul Paris St Germain's all-time goalscoring record as a late strike was officially recorded as an own goal.
Benfica came from a goal behind to beat Atletico Madrid 2-1 at the Vicente Calderon and go top of Group C.
Jose Mourinho's return to former club Porto ended in a 2-1 Champions League defeat as Chelsea's miserable start to the season continued.
Stand-in goalkeeper David Ospina had a night to forget as Arsenal slumped to a 3-2 home defeat against Olympiakos on Wednesday to leave their Champions League hopes in jeopardy.
Late goals from Sergi Roberto and Luis Suarez saved Barcelona's blushes and earned them a valuable win over visitors Bayer Leverkusen in Champions League Group E.
Robert Lewandowski's incredible goal scoring form continued as the striker's hat trick helped Bayern Munich thrash Dinamo Zagreb 5-0.
Belarusian champions BATE Borisov shocked Italian side Roma with a 3-2 win at the Borisov-Arena in Champions League Group E.
Valencia got their Champions League campaign up and running with a 1-0 victory at Lyon in Group H.
Oleg Shatov's second-half goal earned Zenit St Petersburg a 2-1 Champions League victory over Gent at the Petrovsky Stadium on Tuesday night to strengthen their position at the top of Group H.
Goals from Andriy Yarmolenko and Aluisio Junior Moraes gave Dynamo Kiev a 2-0 Champions League victory over Maccabi Tel-Aviv in Group G.
Champions League holders Barcelona saw their perfect start to the season ended after they were held to a 1-1 draw by Roma at the Stadio Olimpico in Wednesday's Group E opener.
Diego Costa scored his first Champions League goal for Chelsea as the beleaguered Premier League champions claimed a much-needed fillip by thrashing Maccabi Tel Aviv at Stamford Bridge.
Arsenal had striker Olivier Giroud sent off as they slumped to a disappointing 2-1 defeat in their Champions League Group F opener at Dinamo Zagreb.
Thomas Muller's scoring streak continued as he netted a brace to steer Bayern Munich to a 3-0 win at Olympiakos in their Champions League Group F opener.
Hakan Calhanoglu scored a brace either side of Javier Hernandez's first goal for Bayer Leverkusen as the German side made a winning start in Champions League Group E by seeing off BATE Borisov 4-1 at home.
Zenit St Petersburg got their Champions League campaign off to a winning start as they recorded a 3-2 victory at Valencia in Wednesday's Group H opener.
Gent fought back to clinch a point in a heroic display after having two men sent off in their first ever Champions League group match which ended 1-1 against Lyon.
Luke Shaw suffered a horrific suspected broken leg as Manchester United's return to the Champions League ended in a disappointing 2-1 defeat to PSV Eindhoven.
Manchester City suffered familiar European wobbles as they surrendered a lead to lose their Champions League Group D opener 2-1 to Juventus.
Cristiano Ronaldo hit a second-half hat trick as Real Madrid opened their Champions League campaign with a 4-0 victory over 10-man Shakhtar Donetsk in Tuesday's Group A showdown at the Santiago Bernabeu.
Angel Di Maria opened his account for Paris Saint-Germain as they began their Champions League Group A campaign with a 2-0 victory over Malmo.
Sevilla scored two second-half penalties and missed another as they defeated Borussia Monchengladbach 3-0 in their opening Champions League group-stage clash.
Antoine Griezmann struck twice in the first half as Atletico Madrid made an ideal start to their Champions League campaign with a 2-0 victory at Galatasaray.
Benfica opened their Champions League campaign with a 2-0 victory over group stage new boys Astana in Lisbon.
Late goals by central defenders Jose Gimenez and Diego Godin earned Atletico Madrid a 2-0 victory over Juventus in their Champions League round-of-16 first leg at the Wanda Metropolitano, amid more video assistant referee (VAR) controversy.
Late goals from Leroy Sane and Raheem Sterling gave Manchester City a 3-2 win at Schalke 04 in their Champions League round of 16 first leg on Wednesday that put the English side in the driving seat.
Liverpool and Bayern Munich cancelled each other out to draw 0-0 in the first leg of their Champions League round-of-16 clash on a tense night at Anfield.
Barcelona were held to a frustrating 0-0 draw at Olympique Lyonnais in their Champions League last-16 first leg on Tuesday as both sides remained unbeaten in this season's competition.
Marco Asensio scored a late winner for Real Madrid in a 2-1 victory at Ajax Amsterdam, who were left to rue a goal disallowed by the video assistant referee (VAR) in their Champions League round-of-16 first leg on Wednesday.
Tottenham Hotspur will take a commanding lead to the Westfalenstadion next month after beating Borussia Dortmund 3-0 in the first leg of their Champions League round-of-16 clash at Wembley.
Goals from Presnel Kimpembe and Kylian Mbappe left Manchester United with a mountain to climb as Paris Saint-Germain won 2-0 at Old Trafford in the Champions League round-of-16 first leg and Paul Pogba was sent off.
Teenager Nicolo Zaniolo scored a quick-fire double to earn AS Roma a 2-1 win against Porto in their Champions League last-16 first leg on Tuesday.
Manchester United will face Paris Saint-Germain in the Champions League round of 16, while Liverpool have been drawn against Bayern Munich.
Manchester City battled back to winning ways, coming from a goal down to overwhelm Hoffenheim 2-1 in the Champions League with a brilliant Leroy Sane double that ensured they progressed to the last-16 as winners of Group F on Wednesday.
Manchester United endured an undignified end to their topsy-turvy Champions League group stage campaign by losing 2-1 at already-eliminated Valencia on Wednesday and missing their chance of topping Group H.
Olympique Lyonnais earned the point they required to book their place in the Champions League last 16 but needed Nabil Fekir's equaliser 20 minutes into the second half to salvage a 1-1 draw away to Shakhtar Donetsk.
Two goals from striker Guillaume Hoarau led Young Boys to a shock 2-1 Champions League win over already-qualified Juventus on Wednesday to hand the Serie A side their first away defeat in a competitive match for over a year.
Striker Robert Lewandowski scored twice as Bayern Munich sealed top spot in Group E following a thrilling 3-3 Champions League draw at Ajax in which both sides ended with 10 men.
Benfica finished its Champions League campaign with a 1-0 win over AEK Athens on Wednesday.
Real Madrid suffered their heaviest ever home defeat in Europe on Wednesday when the already-qualified Spaniards were thumped 3-0 at the Santiago Bernabeu by CSKA Moscow in the Champions League.
Viktoria Plzen beat struggling Roma 2-1 in the Champions League on Wednesday to earn a Europa League spot.
Tottenham Hotspur made it into the round of 16 of the Champions League, coming from behind to grab a 1-1 draw at Barcelona on Tuesday which saw them finish second in Group B at the expense of Inter Milan.
Paris Saint-Germain reached the round of 16 of the Champions League on Tuesday thanks to an inspired performance by their three-pronged attack of Neymar, Edinson Cavani and Kylian Mbappe in a 4-1 win at Red Star Belgrade.
Inter Milan were knocked out of the Champions League after they could only manage a 1-1 draw at home to Group B's bottom club PSV Eindhoven on Tuesday to finish third behind Tottenham Hotspur.
Mohamed Salah's first-half strike gave Liverpool a 1-0 win over Napoli in Champions League Group C action on Tuesday.
An under-strength Borussia Dortmund deepened AS Monaco's season-long misery on Tuesday with a 2-0 away victory that ensured they finished top of Champions League Group A ahead of Atletico Madrid.
Atletico Madrid were denied top place in Group A of the Champions League on Tuesday after a goalless draw away at Club Brugge in Belgium meant they finished second behind Borussia Dortmund.
Alessandro Schoepf's stoppage time goal gave Schalke 04 a 1-0 win over Lokomotiv Moscow in Champions League Group D action on Tuesday.
Porto struggled to a 3-2 away victory over Galatasaray in their final Champions League group match on Tuesday but the Turks stayed third in Group D and secured a spot in the Europa League's round of 32.
Real Madrid midfielder Luka Modric has ended the Cristiano Ronaldo-Lionel Messi stranglehold on the Ballon d'Or.
Two first-half goals gave Paris Saint-Germain a crucial 2-1 Champions League home win over Liverpool, putting them in a great position to qualify and leaving Jurgen Klopp's side, finalists last season, in danger of elimination.
Napoli swept aside Red Star Belgrade with a typically entertaining performance as two goals from Dries Mertens helped them to a 3-1 win over the former European champions in their Champions League match on Wednesday.
Borussia Dortmund booked their spot in the Champions League knockout stage with a game to spare after a goalless draw against visitors Club Brugge in Group A on Wednesday.
Christian Eriksen kept Tottenham Hotspur's hopes of reaching the round of 16 in the Champions League alive when he came off the bench to score a late winner in his side's 1-0 victory over Inter Milan at Wembley on Wednesday.