Ahead of the start of the group stages on Tuesday a look at what is new for the 2018-19 staging of the competition.
Uefa Champions League talking points: Cristiano Ronaldo's fresh challenge, new managers and earlier start times
The Uefa Champions League group stages start on Tuesday night, with eight groups of four sides competing in matches over the next three months to decide who goes through to the last 16.
Ahead of the action beginning, here is a look at the major changes to watch for in the tournament from manager changes to start times.
Ronaldo's to push Juventus cause
Cristiano Ronaldo is the most successful player in the Champions League era of the competition, having won it five times in his career.
The Portuguese forward was part of the Manchester United side that won in 2008 and then he won the tournament with Real Madrid in 2014, 2016, 2017 and this year in May against Liverpool.
He is now with Juventus and if the Serie A champions were to win the competition for the first time since 1996 this season then he would equal Francisco Gento's record of six European Cup winners' medals, which the latter achieved with Real Madrid between 1956 and 1966.
Ronaldo already holds the record for most goals in the Champions League, with 120 goals in 153 appearances.
He will start his first Champions League game for Juventus on Wednesday with a return to Spain as they take on Valencia.
Lopetegui follows on from Zidane
The challenge of following in the footsteps of Zinedine Zidane is the task facing Real Madrid manager Julen Lopetegui.
Despite Real Madrid being inconsistent in La Liga in recent seasons, they have won the Champions League the past three years, the most successful run by any club in the competition in the past 40 years.
Lopetegui's side, who are without Ronaldo now, will look to Gareth Bale and Luka Modric to inspire them this season, with the side in Group G with Roma, Viktoria Plzen and CSKA Moscow.
Lopetegui is not the only new manager in charge of an expected contender. Thomas Tuchel is now in charge of Paris Saint-Germain, while Carlo Ancelotti, who won the Champions League with AC Milan and Real Madrid, is the man overseeing Napoli's hopes.
Earlier start times
Champions League games, other than matches in Russia, were all usually scheduled to kick off at 10.45pm UAE time (11.45pm in the winter months of November to March).
But that is changing, at least until 2020-21, with Uefa having some games now start at 8.55pm UAE time in an attempt to spread the action and allow more matches to be viewed on TV.
On Tuesday, Barcelona v PSV Eindhoven and Inter Milan v Tottenham Hotspur are both being played at 8.55pm, with the night's other fixtures, which include Liverpool v Paris Saint-Germain and Monaco v Atletico Madrid starting at 10.45pm.
On Wednesday, it is Ajax v AEK Athens and Shakhtar Donetsk v Hoffenheim that will be the matches played early.
There are three clubs making their debut in the Uefa Champions League group stages.
There is German side Hoffenheim, who are in Group F with Manchester City, Lyon and Shakhtar Donetsk.
Young Boys of Switzerland are in Group H with former champions Manchester United, Juventus and Spanish side Valencia.
Serbian side Red Star Belgrade are former European Cup winners from 1991, when they represented Yugoslavia, but this will be their first appearance in the group stages format of the competition.
They are in Group C with Liverpool, Napoli and Paris Saint-Germain.