A little over three months have passed since Real Madrid made surprisingly light work of Juventus in a 4-1 win to lift the Champions League trophy for a record 12th time and become the first team to successfully defend their crown in the modern era.
Madrid will have to wait until Wednesday to begin their campaign, but runners-up Juve are among those in action on Tuesday, and things are not going to be much easier for Massimiliano Allegri's men as they head to Barcelona in arguably the game of the round - a repeat of last season's semi-final.
Europa League champions Manchester United make their return to the competition after a year out, as do their Premier League rivals Chelsea, with Basel and Azerbaijani newcomers Qarabag their respective visitors.
Meanwhile, Paris Saint-Germain will unleash Neymar and Kylian Mbappe for the first time in Europe as they travel to Celtic.
Using Opta data, we take a look at some of the best stats ahead of the opening group games on Tuesday.
BENFICA v CSKA MOSCOW
- Benfica have not made it any further than the quarter-finals of the Champions League since 1992-93.
- Benfica and CSKA Moscow's only previous encounter was in the last 32 of the 2004-05 UEFA Cup. The Russian side progressed thanks to a 2-0 home win and 1-1 draw in Lisbon; they went on to lift the trophy later that season.
- CSKA are making their 11th Champions League appearance - their fifth in a row. That is the second most for a Russian side after Spartak Moscow (12).
- CSKA are winless in their last 10 Champions League games (D4 L6), equaling their longest run without a victory in the competition. Away from home, they have lost 11 of their last 13 Champions League games (W1 D1).
- This is Viktor Goncharenko's fourth Champions League campaign as manager, after three previous appearances with BATE Borisov. He was the first manager to lead a Belarusian team into the group stages of the competition.
MANCHESTER UNITED v BASEL
- Basel are unbeaten against United at Old Trafford, having drawn their two trips to North-West England (1-1 in March 2003, 3-3 in September 2011).
- United have reached the knockout stages in 16 of their previous 20 Champions League appearances; however they have not made it past the group stages since 2013-14.
- Basel are winless in their last 10 Champions League games (D4 L6), their longest drought in the competition. They have also not scored more than one goal in those 10 games.
- Jose Mourinho is taking part in the Champions League with a fifth different club after Porto, Chelsea, Inter Milan and Real Madrid. Only Carlo Ancelotti (7), Rafael Benitez and Claudio Ranieri (6) have taken charge of more clubs in the competition.
- Paul Pogba has only scored two goals in 32 Champions League games.
BAYERN MUNICH v ANDERLECHT
- This is the 20th time in the last 21 seasons that Bayern Munich have qualified for the Champions League, the only exception coming in 2007-08. They have reached the semis in six of the last eight seasons.
- Bayern Munich have won 20 of their last 25 Champions League group games (L5), with their last draw coming in November 2012 against Valencia (1-1).
- Anderlecht have never made the knockout stages of the Champions League in their 11 previous participations.
- Robert Lewandowski has scored 40 goals in 61 Champions League games since his debut in the competition in 2011-12. Over that period, only Cristiano Ronaldo (77 goals) and Lionel Messi (57 goals) have found the net on more occasions.
- Anderlecht have won only three of their last 37 Champions League games (D10 L24). They have also only kept four clean sheets in those 37 games.
CELTIC v PARIS SAINT-GERMAIN
- PSG have not progressed further than the quarter-finals in the last five seasons. Their best performance to date is a semi-final in 1994-95 when they were eliminated by AC Milan.
- Neymar has delivered 12 assists over the last two seasons of the Champions League, three more than any other player (Cristiano Ronaldo, 9). He has also had a hand in 10 goals (four goals, six assists) in four Champions League games versus Celtic.
- Dani Alves has more goals (10) and more assists (25) than any other full-back in the Champions League since his debut with Sevilla in 2007-08. He is the second Brazilian to have played in 100 games in the competition after Roberto Carlos.
- Brendan Rodgers has won only one of his 12 group games as manager in the Champions League, with that sole victory coming against Ludogorets (2-1) in September 2014 when he was in charge of Liverpool.
- Celtic have won only one of their last 14 Champions League games (D3 L10), this came in October 2013 against Ajax.
CHELSEA v QARABAG
- This is the first ever competitive encounter between Chelsea and Qarabag. In fact, the only previous meeting between English and Azerbaijani sides saw Tottenham face Qarabag in the 2015/16 Europa League group stages; Spurs won both games (3-1 at home, 1-0 in Baku).
- Qarabag are the only team, alongside RB Leipzig, to make their Champions League debut this season. They are also the first team from Azerbaijan to reach the group stages of the competition.
- Eden Hazard has scored only one goal in his last 12 Champions League games, it was from the penalty spot.
- This is Antonio Conte's third Champions League campaign as manager. His best performance was in 2012-13 when he reached the quarter-finals with Juventus.
- Chelsea have lost only one of their last 13 Champions League group games (W9 D3), away against Porto in September 2015 (1-2). The Blues have also scored in each of their last 24 group games at Stamford Bridge.
ROMA v ATLETICO MADRID
- Roma have won only one of their last 13 Champions league games (D5 L7). That was against Bayer Leverkusen in November 2015 (3-2).
- Roma have also only kept one clean sheet in their last 22 Champions League games (a goalless draw against BATE Borisov in December 2015), conceding a total of 51 goals over that period.
- Diego Simeone's teams have conceded on average 0.67 goals per game in the Champions League (32 in 48 games), the best ratio among managers to have taken charge of 20 or more games in the competition.
- Only Real Madrid have played more Champions League games (51) than Atletico (48) over the last four seasons.
- Antoine Griezmann has scored or assisted 50% of Atletico's goals in the Champions League over the last two seasons (13 goals and 3 assists).
BARCELONA v JUVENTUS
- Barcelona have won 13 of their last 16 Champions League group games (D2 L1). They have also scored in 43 of their last 44 group games, the only exception coming against Benfica in December 2012 (0-0) when Barca were already guaranteed top their group.
- This is Juventus' 18th appearance in the Champions League, a new record for an Italian side ahead of AC Milan (17).
- Lionel Messi has netted 94 goals in the Champions League, the second highest tally in the competition behind Cristiano Ronaldo (105). Ten of his 11 goals last season were scored in the group stages.
- Ernesto Valverde is taking charge of a fourth club in the Champions League after Olympiakos, Valencia and Athletic Bilbao. He has never gone further than the round of 16.
- Massimiliano Allegri has reached the knockout stages in each of his seven campaigns as manager in the Champions League. He was beaten finalist in two of the last three seasons with Juventus.
OLYMPIACOS v SPORTING CP
- Olympiacos are making their 18th appearance in the Champions League, which is twice as many as any other Greek side (Panathinakos, 9). Their best performance came in 1998-99 when they reached the quarter-finals.
- Sporting have lost six of their last seven Champions League games (W1), including their last four. They have never lost five in a row in the competition.
- Olympiacos are the third club Besnik Hasi has managed in the Champions League, after Anderlecht (6 games) and Legia Warsaw (1 game). He has only won one of his seven games so far.
- Sporting are Seydou Doumbia's third club in the Champions League after CSKA Moscow and Basel. With 14 goals, he is the second most prolific Ivorian in the competition after Didier Drogba (44).
- Sporting manager Jorge Jesus has taken charge of 40 games in the Champions League, the second most for a Portuguese manager after Jose Mourinho (133). His best performance dates back to 2011-12 when he reached the quarter-finals with Sporting's bitter rivals Benfica.