The Primeira League is the top tier of professional soccer in Portugal. The league was founded in 1934 as an experimental league and formally adopted and used to crown a national champion in 1938. The league is organized by Liga Portuguesa de Futebol Profissional.
An 18-club league was adopted for the 2014/15 season (up from 16 clubs) and is the current number. Each team plays every other team at home and away for a 34 game season. Teams earn 3 points for a win, 1 point for a draw, and 0 points for a loss. The team with the highest point total at the end of the year is the champion.
The champion and runner-up earn a berth in the group stage of the UEFA Champions League while the 3rd place team is placed in the final Champions League playoff round. The 4th place team enters the UEFA Europa League group stage and the 5th and 6th place teams qualify for the Europa League third qualifying round.
The bottom 2 teams are relegated to the Segunda Liga and replaced by the top 2 non-reserve teams from the Segunda Liga.
The league has been dominated by ‘Os Três Grandes’ (the Big Three) – Benfica, Porto, and Sporting CP (formerly Sporting Lisbon), since the league was formed. The have combined to win all but 2 league championships. Belenenses (1945/46) and Boavista (2000/01) are the only other clubs to win a championship. The Big Three clubs are the only club’s in Portugal to never be relegated to the Segunda Liga.