The 2023–24 UEFA Champions League group stage began on 19 September 2023 and ended on 13 December 2023. A total of 32 teams competed in the group stage to decide the 16 places in the knockout phase of the 2023–24 UEFA Champions League.
Union Berlin and Antwerp made their debut appearance in the group stage. This was the Belgian club's first appearance in the European Cup since their first round exit in the 1957–58 season, and the first ever for the German side. A total of 15 national associations were represented in the group stage.
This was the final season with the group stage format, which was replaced by the league stage format starting from the next season.[1]
The draw for the group stage was held on 31 August 2023, 18:00 CEST, in Monaco. The 32 teams were drawn into eight groups of four. For the draw, the teams were seeded into four pots, each of eight teams, based on the following principles:
Pot 1 contained the Europa League title holders, and the champions of the top seven associations based on their 2022–23 UEFA country coefficients.
Pot 2, 3 and 4 contained the remaining teams, seeded based on their 2022–23 UEFA club coefficients.[2]
Teams from the same association could not be drawn into the same group. Prior to the draw, UEFA formed pairings of teams from the same association (one pairing for associations with two or three teams, two pairings for associations with four or five teams) based on television audiences, where one team would be drawn into Groups A–D and another team would be drawn into Groups E–H, so that the two teams would play on different days. The following pairings were announced by UEFA after the group stage teams were confirmed:[3]
On each matchday, one set of four groups played their matches on Tuesday, while the other set of four groups played their matches on Wednesday, with the two sets of groups alternating between each matchday. The fixtures were decided after the draw, using a computer draw not shown to public. Each team did not play more than two home matches or two away matches in a row, and played one home match and one away match on the first and last matchdays (Regulations Article 16.02).[4]
In each group, teams played against each other home-and-away in a round-robin format. The top two teams of each group advanced to the round of 16. The third-placed teams were transferred to the Europa League knockout round play-offs, while the fourth-placed teams were eliminated from European competitions for the season.
Teams were ranked according to points (3 points for a win, 1 point for a draw, 0 points for a loss). If two or more teams were tied on points, the following tiebreaking criteria were applied, in the order given, to determine the rankings (see Article 17 Equality of points – group stage, Regulations of the UEFA Champions League):[5]
Points in head-to-head matches among the tied teams;
Goal difference in head-to-head matches among the tied teams;
Goals scored in head-to-head matches among the tied teams;
If more than two teams were tied, and after applying all head-to-head criteria above, a subset of teams were still tied, all head-to-head criteria above were reapplied exclusively to this subset of teams;
Goal difference in all group matches;
Goals scored in all group matches;
Away goals scored in all group matches;
Wins in all group matches;
Away wins in all group matches;
Disciplinary points (direct red card = 3 points; double yellow card = 3 points; single yellow card = 1 point);
The fixtures were announced on 2 September 2023, two days after the draw. The matches were played on 19–20 September, 3–4 October, 24–25 October, 7–8 November, 28–29 November and 12–13 December 2023. The scheduled kick-off times were 18:45 (two matches on each day) and 21:00 (remaining six matches) CET or CEST.
Times are CET or CEST,[note 1] as listed by UEFA (local times, if different, are in parentheses).
^ abTied on head-to-head points, goal difference, and goals scored. Goal difference in all matches: Real Sociedad +5, Inter Milan +3.
^ abTied on head-to-head points, goal difference, goals scored, and goal difference in all matches. Goals scored in all matches: Benfica 7, Red Bull Salzburg 4.
Manchester City and Manchester United
Sevilla and Atlético Madrid
Napoli and Lazio
Bayern Munich and Borussia Dortmund
Paris Saint-Germain and Lens
Benfica and Porto
Feyenoord and PSV Eindhoven
Bayern Munich 
Copenhagen 
Galatasaray 
Manchester United 
PSV Eindhoven 
Lens 
Sevilla 
Napoli 
Braga 
90+4'
Red Bull Salzburg 
Celtic 
Young Boys 
Red Star Belgrade