The UEFA Champions League (usually referred to as simply the Champions League or historically as the European Cup) is an annual association football cup competition organised by UEFA since 1955 for the top football clubs in Europe. It is the most prestigious club trophy in European football, and is widely considered the most prestigious club trophy in the world.

Prior to 1992 the tournament was officially called the European Champion Clubs' Cup but was usually referred to as simply the European Cup or European Champions' Cup. The competition was initially a straight knockout competition open only to the champion club of each country. During the 1990s the tournament began to be expanded, incorporating a round-robin group phase and more teams. Europe's strongest national leagues now provide up to four teams each for the competition. The UEFA Champions League should not be confused with the UEFA Europa League, formerly known as the UEFA Cup.

The tournament consists of several stages. In the present format it begins in mid-July with three knockout qualifying rounds. The 16 surviving teams join 16 seeded teams in the group stage, in which there are eight groups consisting of four teams each. The eight group winners and eight runners-up enter the final knockout phase, which ends with the final match in May.

The title has been won by 21 different clubs, 12 of which have won the title more than once. The all-time record-holders are Real Madrid, who have won the competition nine times, including the first five seasons it was contested. Barcelona are the current champions. Since the tournament changed name and structure in 1992, no club has managed consecutive wins.