[1] It began on 30 June 2011 with the first legs of the first qualifying round, and ended on 9 May 2012 with the final held at Arena Națională in Bucharest, Romania.

[2] As part of a trial that started in the 2009–10 UEFA Europa League, two extra officials – one on each goal line – were used in all matches of the competition from the group stage.

[3] Atlético Madrid won the title, defeating Athletic Bilbao 3–0 in an all-Spanish final.

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.

When a place is vacated, it is redistributed within the national association by the following rules:[6] The labels in the parentheses show how each team qualified for the place of its starting round:[9][10] All draws held at UEFA headquarters in Nyon, Switzerland unless stated otherwise.

[8] Matches in the qualifying, play-off, and knockout rounds may also be played on Tuesdays or Wednesdays instead of the regular Thursdays due to scheduling conflicts.

If two or more teams are equal on points on completion of the group matches, the following criteria are applied to determine the rankings (in descending order):[6] A total of 24 national associations are represented in this group stage (including Scotland after Celtic were reinstated into the Europa League over Sion), with England having the most teams, with four.

In the knockout phase, teams play against each other over two legs on a home-and-away basis, except for the one-match final.

In the draws for the round of 16 onwards, there are no seedings, and teams from the same group or the same association may be drawn with each other.