The Clube Atlético Mineiro, the oldest active football club in Minas Gerais, was founded on 25 March 1908 by twenty-two students from Belo Horizonte.

The competition was organised by the Federação Brasileira de Foot-Ball, a federation for professional clubs that would later merge into the Brazilian Sports Confederation (CBD).

[30] The tournament, the country's first annual nationwide competition, was a cup contested between state league champions, originally created by the CBD to select Brazil's entrants in the newly formed Copa Libertadores.

[33] With the arrival of Telê Santana as the club's head coach in 1970, Galo broke Cruzeiro's sequence and won its first state league title in the Mineirão,[34] also finishing third in the last Roberto Gomes Pedrosa.

[37][38] Reinaldo, Toninho Cerezo, Éder, Luizinho, Paulo Isidoro and João Leite, players who represented Brazil at international level, were central to the team that took Atlético to six consecutive state league victories between 1978 and 1983, and to good results in the Série A.

In a repetition of the previous year's Brasileiro decisive match, the opponent in the final of this competition was São Paulo, with Atlético this time winning a penalty shootout.

[43][44][45] The team was then eliminated from the following year's Copa Libertadores undefeated, in another decisive match marked by controversy: a play-off against Flamengo that ended after 37 minutes, following the sendings-off of five Atlético players.

[24] Atlético was one of Brazil's top sides of the 1980s, providing many players to the Brazilian national team, being dominant at state level and having good performances in the Brasileiro, but a tendency to lose in its final knockout stages prevented a new title in this competition.

[52] As champion of that competition, the club took part in the 1993 Copa de Oro, in which it eliminated local rival Cruzeiro in the semi-finals but eventually lost to Argentina's Boca Juniors.

Another triumph came in the 1997 Copa CONMEBOL, when an Atlético team that included Marques and Cláudio Taffarel defeated Argentina's Lanús in the finals, and won the trophy for a second time.

[56] In 1999, after another Campeonato Mineiro title, a Galo side led by Marques and Guilherme, the top scorer in the league, reached the Série A finals for the fourth time, but lost to Corinthians.

The following year, despite a good performance in the Brasileirão with a squad that included Marques, Guilherme and Gilberto Silva, the team was eliminated in the competition's semi-finals, eventually finishing in fourth place.

After an unsuccessful year in 2011, coming close to relegation, the arrival of Cuca as head coach at the end of that season marked the beginning of another successful era for the club.

The arrival of Ronaldinho in the middle of the season was an important event for the club,[63][64] which eventually finished as runner-up in the Série A and earned a spot in the following year's Copa Libertadores.

The quarter-finals of that season's Copa Libertadores saw an iconic moment for Atlético, when a penalty kick was awarded to Mexican Club Tijuana in injury time.

[66][67][68] Atlético then defeated Argentina's Newell's Old Boys in the semi-finals and Olimpia in the finals, both on penalties, after losing both first legs by 2–0 and winning the second ones by the same score, to achieve its first Copa Libertadores title.

[84] In 1945, Fernando Pierucetti, known as Mangabeira, a cartoonist for the A Folha de Minas newspaper, was selected to design mascots for each of the three biggest clubs in Belo Horizonte.

[85][86] Over the years, the word galo (Portuguese for "rooster") became a cheering chant for the supporters and a nickname by which they referred to the club, an appellation that eventually spread to other football fans in the country.

[108] The club's main ground for most of its early years, however, was the Presidente Antônio Carlos stadium, which held 5,000 people; it was nicknamed Estádio de Lourdes for the quarter in which it was located.

[109] The stadium fell out of favor when the larger Independência was built in 1950, and remained largely unused by the first team; eventually it was sold by the club to the Belo Horizonte municipality in the 1960s.

[20] Mineirão (officially Estádio Governador Magalhães Pinto) opened in 1965 and quickly became Galo's new home,[113] as its peak capacity of over 100,000 spectators surpassed any other stadium in Belo Horizonte or in Minas Gerais.

[124] Atlético Mineiro was founded by upper-class students, but from an early age it opened its doors to players from every social class, nationality or ethnicity, which earned it a "people's club" status in Belo Horizonte and in the state.

[125] According to a 2014 survey conducted by IBOPE and Lance!, the club is the second best-supported in Belo Horizonte and in Minas Gerais and has the eighth largest fanbase in Brazil, with over five million supporters.

[126] Galoucura has historically developed alliances with other torcidas in Brazil, most notably Palmeiras's Mancha Verde and Vasco da Gama's Força Jovem.

[136][137] Atlético launched TV Galo in 2007, a premium television channel that provides content for fans such as interviews with players and staff, coverage of training sessions and matches, footballing news, and other themed programming.

The rivalry developed in the 1980s, rising from numerous tendentious events and controversial encounters between the two clubs in Campeonato Brasileiro and Copa Libertadores editions of the period.

[164] Season ticket-holders and participants of the Galo na Veia affiliation programme, called sócios-torcedores, are not full club associates and cannot vote or be elected.

[191] In 2000, the sponsorship deal with Pax de Minas ended and Atlético's professional senior futsal team folded in the following year, with the youth sectors remaining.

[193] In March 2018, the club announced the creation of an American football team, a three-year partnership with Grupo Sada and BH Eagles, named Galo Futebol Americano.

[194][195] In its first season playing with this name in the Superliga Nacional de Futebol Americano, Brazil's American football league, the team won the Southeast Conference undefeated, and proceeded to win all matches in the playoffs, including the Brasil Bowl against João Pessoa Espectros.