The 1991 season of the Campeonato Brasileiro began on February 2, 1991, and reached its end on June 9, 1991. The competition was won by São Paulo. Santos Futebol Clube's Paulinho McLaren, with 15 goals, was the competition's top goal scorer.

It was contested by 20 teams, and São Paulo won the championship. 20 teams played against each other once in the first stage. The four best-placed teams qualified to the semi-finals, played in two legs. The semi-final winners qualified to the final, played in two legs.

São Paulo: Zetti; Cafu, Antônio Carlos, Ricardo Rocha and Leonardo; Ronaldão, Bernardo and Raí; Müller, Macedo and Elivélton (Mário Tilico). Head coach: Telê Santana.

Bragantino: Marcelo; Gil Baiano, Júnior, Nei and Biro-Biro; Mauro Silva, Alberto and Mazinho Oliveira; Ivair (Luís Müller), Sílvio and Ronaldo Alfredo (Franklin). Head coach: Carlos Alberto Parreira.

Bragantino: Marcelo; Gil Baiano, Júnior, Nei and Biro-Biro; Mauro Silva, Alberto and Mazinho Oliveira; Ivair (Luís Müller), Sílvio and João Santos (Franklin). Head coach: Carlos Alberto Parreira.

The Campeonato Brasileiro de Clubes da Série A (Portuguese pronunciation: [ˈsɛɾji ˈa]), popularly known as the Brasileirão (pronounced: [bɾazilejˈɾɐ̃w]), is a professional football league at the top of the Brazilian football league system held annually since 1971. Contested by twenty clubs, it operates a system of promotion and relegation with the Série B. The season runs from May to December of the same year, with teams playing 38 matches each, totalling 380 matches in the season. Due to sponsorship reasons, the league is known as the Brasileirão Petrobras.

Due to historical peculiarities and the large geographical size of the country, Brazil has a relatively short history of nation-wide football competitions. The modern Campeonato Brasileiro only started in 1971, supported by the military regime of the time and made easier by the advancements in civil aviation and air transport. Before the establishment of a national league the most prestigious football competitions in Brazil were the state leagues, notably the Campeonato Paulista and Campeonato Carioca state championships (the tournaments of São Paulo and Rio de Janeiro states). Most state competitions have a much longer history than the national competition and, consequently, the various state leagues were considered more prestigious than the national league during the first years.

Serie A (Italian pronunciation: [ˈsɛːrje ˈa]), also called Serie A TIM due to sponsorship by Telecom Italia, is a professional league competition for football clubs located at the top of the Italian football league system and has been operating for over eighty years since the 1929-30 season. It had been organized by Lega Calcio until 2010, but a new league, the Lega Serie A, had been created for the 2010–11 season. Serie A has produced the highest number of European Cup finalists: Italian clubs have reached the final of the competition on a record twenty-six different occasions, winning the title twelve times. Serie A is ranked 4th among European leagues according to UEFA's league coefficient behind the English Premier League, Spanish La Liga, and German Bundesliga, which is based on the performance of Italian clubs in the Champions League and the Europa League. It also ranked 5th in world according to the first trends of the 2011 IFFHS rating.

In its current format, the Italian Football Championship was revised from having regional and interregional rounds, to just one solid league from the 1929–30 season onwards; the Serie A system carries on today. The championship titles won before 1929 are officially recognised by FIGC as a championship in the same way the ones since then are. The 1945–46 season, when the league was played over two geographical groups due to WWII destructions, is not statistically considered, even if its title is fully official.