The Brazilian Naval Revolts (Portuguese: Revoltas da Armada, lit. 'Navy's Revolt') were armed mutinies promoted mainly by admirals Custódio José de Melo and Saldanha da Gama and their fleet of rebel Brazilian navy ships against the claimed unconstitutional staying in power of president Floriano Peixoto.

The revolts had a number of causes: "personal animosities in the ruling elite; friction in federal-state relations and between the president and Congress; militarism; government extravagance; army navy rivalry; and some lingering monarchical sentiments following the overthrow of the empire in 1889."

The United States supported the incumbent government against the insurgents.

In November 1891, President Marshal Deodoro da Fonseca, amid a political crisis compounded by the effects of an economic crisis, in flagrant violation of the new constitution, decided to "solve" the political crisis by ordering the closure of Congress, supported mainly by the Paulista oligarchy. The Navy, still resentful of the circumstances and outcomes of the coup that had put an end to the monarchy in Brazil, under the leadership of admiral Custódio José de Melo, rose up and threatened to bombard the city of Rio de Janeiro, then the capital of Brazil. To avoid a civil war, marshal Deodoro resigned the presidency in 23 November. With the resignation of Deodoro, after just nine months from the beginning of his administration, vice president Floriano Peixoto took office. The 1891 Constitution, however, provided for a new election if the presidency or vice-presidency became vacant sooner than two years in office. The opposition then accused Floriano of staying as head of the nation illegally.

The second revolt started in March 1892, when thirteen generals sent a letter and manifesto to the President Marshal Floriano Peixoto. This document demanded new elections be called to fulfill the constitutional provision and ensure internal tranquility in the nation. Floriano harshly suppressed the movement, ordering the arrest of their leaders. Thus, not legally solved, the political tensions increased. The revolt broke out in September 1893 at Rio de Janeiro, and was suppressed only in March 1894 after a long blockade of the city.

With many of the Brazilian Navy's most powerful ships either in the hands of the rebels or under repair, the Brazilian government had to improvise a new fleet to battle the rebel fleet. The "paper fleet", as it was called, had to face off against a mutiny that had overtaken most of the powerful ships of the original navy. Local bloody conflicts in some regions of Brazil ensued. The navy's mutiny off Rio de Janeiro, in the Guanabara Bay, was also a challenge, and became linked to the Federalist Revolution in southern Brazil.

The revolt included the powerful battleship Aquidabã and a collection of small ironclads, modern cruisers and older wood "cruiser" or steam frigate type ships. Two of the navy's major ships were overseas and supposedly away from the conflict: the battleship Riachuelo was under repairs in France, and the corvette Barroso was on a round-the world training voyage (during which she sank). This did not leave the government with much left to challenge the mutineers, who could have controlled the seas and influenced the concurrent conflicts on land.

The government basically bought itself a new naval force on the open market, of small and sometimes unusual ships including torpedo gunboats, various medium and small torpedo boats, small armed yachts, and a transport converted to carry a Zalinski dynamite gun (a pneumatic gun launching a dynamite charge of massive explosive force and marginal accuracy). Such improvised stocking up was common at that time: the US pressed a similar mix of ships into action to supplement its fleet in the 1898 war with Spain (or to buy them before Spain could), and Japan also scrambled to purchase available ships for its conflict with Russia in 1904-5. In this case, however, the new fleet was dedicated to confronting the original navy of the same country.