A tournament is a competition involving a relatively large number of competitors, all participating in a sport or game. More specifically, the term may be used in either of two overlapping senses:

These two senses are distinct. All golf tournaments meet the first definition, but while match play tournaments meet the second, stroke play tournaments do not, since there are no distinct matches within the tournament. In contrast, football (soccer) leagues like the Premier League are tournaments in the second sense, but not the first, having matches spread across many stadia over a period of up to a year. Many tournaments meet both definitions; for example, the Wimbledon tennis championship.

The 2011–12 UEFA Champions League was the 57th season of Europe's premier club football tournament organised by UEFA, and the 20th season in its current UEFA Champions League format. As part of a trial that started in the 2009–10 UEFA Europa League, two extra officials – one behind each goal – were used in all matches of the competition from the play-off round.

The final was held at the Allianz Arena in Munich, Germany.Chelsea's caretaker manager Roberto Di Matteo led the club to win their first UEFA Champions League title after beating Bayern Munich 4–3 on penalties in the final. They earned a berth at the 2012 FIFA Club World Cup and 2012 UEFA Super Cup. Barcelona were the defending champions, but were eliminated by the eventual winners Chelsea in the semi-finals.

Association team allocation

A total of 76 teams participated in the 2011–12 Champions League from 52 UEFA associations (Liechtenstein organises no domestic league competition). Associations are allocated places according to their 2010 UEFA country coefficients, which takes into account their performance in European competitions from 2005–06 to 2009–10.

This article details the 2011–12 UEFA Champions League group stage.

The group stage featured 32 teams: the 22 automatic qualifiers and the 10 winners of the play-off round (five through the Champions Route, five through the League Route).

The teams were drawn into eight groups of four, and played each other home-and-away in a round-robin format. The matchdays were 13–14 September, 27–28 September, 18–19 October, 1–2 November, 22–23 November, and 6–7 December 2011.

The top two teams in each group advanced to the first knockout round, while the third-placed teams dropped down to the Europa League round of 32.

Seeding

The draw for the group stage was held at Grimaldi Forum, Monaco on 25 August 2011 at 17:45 CEST (UTC+02:00).

Teams were seeded into four pots based on their 2011 UEFA club coefficients. The title holders, Barcelona, were automatically seeded into Pot 1. Pot 1 held teams ranked 1–9, Pot 2 held teams ranked 10–24, Pot 3 held teams ranked 31–83, while Pot 4 held teams ranked 86–200 and unranked teams.