The Brazilian Catholic Apostolic Church (Portuguese: Igreja Católica Apostólica Brasileira, pronounced [iˈɡɾeʒɐ kaˈtɔlikaposˈtɔlikɐ bɾaziˈlejɾɐ]; ICAB) is an Independent Catholic Christian church established in 1945 by excommunicated Brazilian Catholic bishop Carlos Duarte Costa. The Brazilian Catholic Apostolic Church is the largest Independent Catholic church in Brazil, with 560,781 members as of 2010, and 26 dioceses as of 2021; internationally, it has an additional 6 dioceses and 6 provinces. It is governed by a president bishop and the Episcopal Council. The church's administration is in Brasilia, Brazil.

The Brazilian Catholic Apostolic Church is the mother church of an international communion called the Worldwide Communion of Catholic Apostolic Churches, though there is no evidence of any recent activity. It is also a primary source of many claims to apostolic succession and the historic episcopate throughout the independent sacramental movement.

Carlos Duarte Costa was an outspoken critic of the regime of Brazilian president Getúlio Vargas (1930–1945) and of the Vatican's alleged relationship with fascist regimes. He also publicly criticized the dogma of papal infallibility and Catholic doctrines on divorce and clerical celibacy. As a result of his outspoken views, Costa resigned from his office of bishop of Botucatu in 1937 and was appointed to a titular see.

In 1940, Cardinal Sebastião da Silveira Cintra, archbishop of Rio de Janeiro, permitted Costa—as titular bishop of Maura—to co-consecrate Bishop Eliseu Maria Coroli. Costa continued to criticize the government and the Roman Catholic Church, advocating policies that were regarded by the authorities as Communist. In 1944, the federal Brazilian government imprisoned him, but later freed him under political pressure from the United States and Great Britain.

In June 1945, Costa established the Brazilian Catholic Apostolic Church (ICAB). Costa's act of schism resulted in his automatic excommunication from the Catholic Church. Later Costa was declared a vitandus—a person to be avoided by Catholics—and those Catholics who became adherents of the ICAB were excommunicated also. According to Peter Anson, Costa was excommunicated "for attacks against the papacy."

In 1949, the Brazilian government temporarily suppressed all public worship by the ICAB, because its liturgy and its clerical attire would result in confusion by being indistinguishable from those of the Catholic Church in Brazil and were tantamount to deception of the public. During the initial months of the Brazilian Catholic Apostolic Church, Costa consecrated Salomão Barbosa Ferraz of the Free Catholic Church.

Ferraz would then leave the Brazilian Catholic Apostolic Church in 1958. Ferraz reconciled with the Catholic Church in 1959 and his episcopal consecration was recognized as valid. However, Ferraz was excluded from church affairs such as the Roman Synod of 1960, even though he was present in Rome at the time, while the Vatican belatedly questioned the legitimacy of having recognized his status.

Shortly thereafter, in 1961, Costa died and the ICAB underwent several years of tumult as dissensions, schisms, and multiple claimants to the throne threw the church into disarray. After this period, the church found stability and growth under Luis Fernando Castillo Mendez, who would be accepted as Costa's successor.