The UEFA Champions League is a seasonal football competition established in 1955. Prior to the 1992–93 season, the tournament was named the European Cup. The UEFA Champions League is open to the league champions of all UEFA (Union of European Football Associations) member associations (except Liechtenstein, which has no league competition), as well as to the clubs finishing from second to fourth position in the strongest leagues. Originally, only the champions of their respective national league and the defending champions of the competition were allowed to participate.
https://en.wikipedia.org/wiki/List_of_European_Cup_and_UEFA_Champions_League_finals