The Campeonato Brasileiro Série A, commonly referred to as the Brasileirão, and also known as Brasileirão Betano due to sponsorship with Betano, is a Brazilian professional league for men's football clubs. At the top of the Brazilian football league system, it is the country's primary football competition. Contested by 20 clubs, it operates on a system of promotion and relegation with the Campeonato Brasileiro Série B. In 2021, the competition was chosen by the IFFHS as the strongest national league in South America as well as the strongest in the world.

In sports leagues, promotion and relegation is a process where teams can move up and down between multiple divisions arranged in a hierarchical structure, based on their performance over a season. Leagues that use promotion and relegation systems are often called open leagues. In a system of promotion and relegation, the best-ranked team(s) in a lower division are promoted to a higher division for the next season, and the worst-ranked team(s) in the higher division are relegated to the lower division for the next season. During the season, teams that are high enough in the league table that they would qualify for promotion are sometimes said to be in the promotion zone, and those at the bottom are in the relegation zone.