Treble (association football)
This list has clubs who have won their country's highest level league and the primary cup competition (the double), as well as the main continental tournament, all in the same season. Celtic was the first club to do this in 1967. They won the Scottish Football League, Scottish Cup, and European Cup. They also won the Scottish League Cup that year. This makes them the only team in history to win the domestic treble and the European Cup in the same season (although most European nations do not have a League Cup).