The Primeira Liga (Portuguese: [pɾiˈmɐjɾɐ ˈliɣɐ]; English: Premier League), also known as Liga NOS for sponsorship reasons, is the top professional association football division of the Portuguese football league system. It is organised and supervised by the Liga Portuguesa de Futebol Profissional. As of the 2014–15 season, the Primeira Liga is contested by 18 teams, with the two lowest placed teams relegated to the Segunda Liga and replaced by the top-two non-reserve teams from this division. Founded in 1934 as an experimental league called Campeonato da Liga, it was officialised in 1938 and named Primeira Divisão (First Division) until 1999, when it was Primeira Liga. A total of 70 teams have competed in the Primeira Liga, but only five have been crowned champions. Among them, the "Big Three" – Benfica (36 titles), Porto (27) and Sporting CP (18) – have won all but two Primeira Liga titles; the other winners are Belenenses (1945–46) and Boavista (2000–01).