The 1964 Brazilian coup d'tat (Portuguese: Golpe de estado no Brasil em 1964), colloquially known in Brazil as the Coup of 64 (Golpe de 64), was a series of events in Brazil from March 31 to April 1 that led to the overthrow of President Joo Goulart by members of the Brazilian Armed Forces, supported by the United States government. The following day, with the military already in control of the country, the speaker of the Brazilian Congress came out in support of the coup and endorsed it by declaring vacant the office of the presidency (though Goulart never officially resigned). The coup put an end to the government of Goulart (also known as 'Jango'), a member of the Brazilian Labour Party, who had been democratically elected vice president in the same election in which conservative Jnio Quadros, from the National Labour Party and backed by the National Democratic Union, won the presidency.

Quadros had resigned in 1961, the same year of his inauguration, in a clumsy political maneuver to increase his popularity. Quadros anticipated that mass demonstrations would demand his return to office and strengthen his position, but he miscalculated. With the presidency vacant and according to the Brazilian Constitution, Quadros should have automatically been replaced by Goulart. Goulart, however, was on a diplomatic trip to the People's Republic of China at the time and, although a moderate nationalist, Goulart was accused of being a communist by right-wing militants, who tried to prevent him from taking office. After lengthy negotiations, led mainly by Tancredo Neves, Goulart's supporters and the right-wing reached an agreement under which the parliamentary system would replace the presidential system in the country. Goulart would continue as head of state, although weakened, and Neves would be named the prime minister.

In 1963, however, a referendum re-established the presidential system with Goulart as president. He took office with full powers, and during his rule several problems in Brazilian politics became evident, as well as disputes in the context of the Cold War, which helped destabilize his government. The Basic Reforms Plan (Reformas de Base) proposed by Goulart had the potential to socialize the profits of large companies. It was labelled as a "socialist threat" by right-wing sectors of society and of the military, which organized major demonstrations against the government in the Marches of the Family with God for Freedom (Marchas da Famlia com Deus pela Liberdade).The coup brought to Brazil a military regime politically aligned to the interests of the United States government. This military dictatorship in Brazil lasted for 21 years, until 1985, when Neves was indirectly elected the first civilian president of Brazil since the 1960 elections.

Jânio da Silva Quadros (Portuguese pronunciation: [ˈʒɐ̃niu dɐ ˈsiwvɐ ˈkwadɾus] (listen); January 25, 1917 – February 16, 1992) was a Brazilian lawyer and politician who served as the 22nd president of Brazil from January 31 to August 25, 1961, when he resigned from office. He also served as the 24th and 36th mayor of São Paulo, and the 18th governor of the state of São Paulo. Quadros was known for his populist style of government, honesty, and eccentric behavior. As president, he focused on economic reform and attempted to root out corruption. He also pursued an independent foreign policy, trying to balance relations between the United States and the Eastern Bloc. Although he was elected by a huge margin, his term was marked by uncertainty and political instability, culminating in his resignation. That unexpected move caused national chaos, with the presidency being assumed by João Goulart.