Champions League is the yearly European club competition that determines the continental champion of Europe. It is the most prestigious competition in world football and one of the most watched events in sports. It is also one of the most lucrative. Real Madrid, with fifteen titles and counting, is the most successful team in Champions League history. Other prestigious clubs with multiple wins include Barcelona, Bayern Munich, Ajax, AC Milan, Liverpool, Manchester United and Internazionale (a.k.a. Inter Milan; Italy).

The inaugural tournament, then known as the European Champion Clubs’ Cup and later as the European Cup, had just six teams. It was a round-robin format, with teams playing each other twice, once at home and once away. Teams earned three points for a win and two for a tie. The winner and runner-up of each group advanced to the semi-finals and final.

In 1960, the tournament expanded to thirty-two teams and kept the rest of the format the same. In 1992, it was renamed to UEFA Champions League and changed the group stage to a double-round-robin format. During this phase, a randomized draw placed teams into eight groups of four and a coefficient-based seeding system was used to create competitive balance.

The knockout stage consisted of the traditional four two-legged rounds prior to the final at a neutral venue, and each match was played in midweek. The new format was introduced in order to create more synergy between the league and knockout phases, and give fans the opportunity to see top European matches on Tuesdays and Wednesdays.