the campeonato paulista série a1, commonly known as campeonato paulista, nicknamed paulistão, is the top-flight professional football league in the brazilian state of são paulo. run by the fpf, the league is contested between 16 clubs and typically lasts from january to april. rivalries amongst four of the most well-known brazilian teams (corinthians, palmeiras, santos and são paulo) have marked the history of the competition. the campeonato paulista is the oldest established league in brazil, being held since 1902 and professionally since 1933.