The 2009 Campeonato Brasileiro de Clubes da Série A was the 39th season of the Série A, the top-level of professional football in Brazil. It was contested by 20 clubs starting on May 9 and ending on December 6. The 2009 edition was won by Flamengo.

The first goal of the tournament was scored by Igor on the 13th minute of the match between his team, Sport and Barueri, which ended in a 1–1 draw. Holders São Paulo had a bad start losing to Fluminense 1–0.

Internacional led the tournament from round 2 to 6, when Atlético Mineiro took the lead. In the 9th round, Internacional regained the lead but one round later Atlético Mineiro managed to come back to the top of the table after defeating their city rivals Cruzeiro 3–0. The club from Belo Horizonte held the lead until round 15, when Palmeiras reached the top. In the middle of the championship, Flamengo was only on the 10th position.

Palmeiras managed to stay in the top until round 34, when they lost 1–0 against Fluminense, which was struggling to avoid relegation. Four days earlier, São Paulo had tied 1–1 with Grêmio after having three players sent off.

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.