Rio de Janeiro Navy Arsenal (Arsenal de Marinha do Rio de Janeiro)

The Rio de Janeiro Navy Arsenal (Arsenal de Marinha do Rio de Janeiro, AMRJ) is a military organization of the Brazilian Navy on Ilha das Cobras, in Guanabara Bay at Rio de Janeiro. It is the Navy's principal maintenance centre and naval base, and is closed to the public. Command is held by a contra-almirante.

The Arsenal covers the design, construction and maintenance of surface ships and submarines for the Brazilian Navy and for foreign navies. Shipbuilding work is undertaken on both military and industrial grounds: mastery of construction technologies and reduction of dependence on foreign suppliers, and the nationalisation of components with corresponding support to domestic industry. Construction output has included the Inhaúma-class corvettes Inhaúma and Jaceguai. Repair work has extended to foreign units, among them major hull work on the Argentine submarine ARA Santa Cruz, which required cutting the pressure hull.

The installation originates in the Arsenal of Rio de Janeiro, established on 29 December 1763 at the foot of the hill of São Bento by the governor-general of Brazil, António Álvares da Cunha, 1st Count da Cunha, for the repair of Portuguese Navy ships. It expanded onto Ilha das Cobras from 1820 and, after Brazilian independence, was reorganised for the new national navy, building warships during the Paraguayan War. Two separate establishments, the Arsenal de Marinha da Ilha das Cobras and the Arsenal de Marinha do Rio de Janeiro, coexisted in 1938; after 1948 only the Ilha das Cobras yard remained, taking the AMRJ designation it holds today.