The UEFA Champions League (abbreviated as UCL) is an annual club football competition organised by the Union of European Football Associations (UEFA) and contested by top-division European clubs, deciding the competition winners through a group and knockout format. 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 (and, for some nations, one or more runners-up) of their national associations. Introduced in 1955 as the European Champion Clubs' Cup, commonly known as European Cup, it was initially a straight knockout tournament open only to the champions of Europe's domestic leagues, with its winner reckoned as the European club champion. The competition took on its current name in 1992, adding a round-robin group stage in 1991 and allowing multiple entrants from certain countries since 1997. It has since been expanded, and while most of Europe's national leagues can still only enter their champion, the strongest leagues now provide up to four teams. Clubs that finish next-in-line in their national league, having not qualified for the Champions League, are eligible for the second-tier UEFA Europa League competition, and from 2021, teams not eligible for the UEFA Europa League will qualify for a new third-tier competition called the UEFA Europa Conference League. In its present format, the Champions League begins in late June with a preliminary round, three qualifying rounds and a play-off round, all played over two legs. The six surviving teams enter the group stage, joining 26 teams qualified in advance. The 32 teams are drawn into eight groups of four teams and play each other in a double round-robin system. The eight group winners and eight runners-up proceed to the knockout phase that culminates with the final match in late May or early June. The winner of the Champions League qualifies for the following year's Champions League, the UEFA Super Cup and the FIFA Club World Cup. In 2020, the traditional schedule for UEFA matches was disrupted due to the impact of the COVID-19 pandemic. The format of the remainder of the tournament was temporarily amended as a result, with the quarter-finals and semi-finals being played as single match knockout ties at neutral venues in Lisbon, Portugal from 12 to 23 August. Spanish clubs have the highest number of victories (18 wins), followed by England (13 wins) and Italy (12 wins). England has the largest number of winning teams, with five clubs having won the title. The competition has been won by 22 clubs, 12 of which have won it more than once. Real Madrid is the most successful club in the tournament's history, having won it 13 times, including its first five seasons. Bayern Munich are the reigning champions, having beaten Paris Saint-Germain 1–0 in the 2020 final.