The UEFA Champions League is an annual club association football competition organised by the Union of European Football Associations (UEFA) and contested by top-division European clubs, deciding the competition winners through a round robin group stage to qualify for a double-legged knockout format, and a single leg final. It is the most-watched club competition in the world and the third most-watched football competition overall, behind only the UEFA European Championship and the FIFA World Cup. It is one of the most prestigious football tournaments in the world and the most prestigious club competition in European football, played by the national league champions of their national associations.

Association football, commonly known as football, or soccer, is a team sport played between two teams of 11 players each, who primarily use their feet to propel a ball around a rectangular field called a pitch. The objective of the game is to score more goals than the opposing team by moving the ball beyond the goal line into a rectangular-framed goal defended by the opposing team. Traditionally, the game has been played over two 45-minute halves, for a total match time of 90 minutes. With an estimated 250 million players active in over 200 countries and territories, it is the world's most popular sport.