Tamandaré da Laje Fort, Fort on Ilha da Laje, Rio de Janeiro, Brazil

Tamandaré da Laje Fort is a military fortress standing on a small island in Guanabara Bay, positioned directly across from Sugar Loaf Mountain. The structure features heavy stone walls and gun placements designed to control shipping traffic entering and leaving the bay.

The fort was built starting in 1644 as part of Portuguese efforts to secure Guanabara Bay against pirates and invaders. It became a crucial defense point protecting Rio de Janeiro from seaborne attacks during colonial times.

The fort's name honours Admiral Joaquim Marques Lisboa, Marquis of Tamandaré, patron of the Brazilian Navy; the Army renamed it by decree on 12 October 1953. Its cannons, corroded by salt air, and the steel cupolas fitted between 1896 and 1906 remain visible on the stonework.

The fort stands on the Laje islet about three kilometres from Urca beach, on the right side of the Guanabara Bay entrance. It was deactivated in 1997 and is now the responsibility of the Army's Centro de Capacitação Física in Urca; it has no heritage listing at municipal, state or federal level and is in a precarious state of conservation, with salt-corroded parts and rusted cannons. There is no regular public access or visitor infrastructure, so it can only be seen from the water or from the Urca shoreline.

In 1836 the fort held Farroupilha leader Bento Gonçalves and Pedro Boticário. On 15 March 1837 both tried to escape, but Pedro Boticário, being very fat, could not get through a window; Bento Gonçalves gave up out of solidarity and both were soon transferred to other prisons.