The Brazilian ironclad Rio de Janeiro was an armored gunboat (Portuguese: Canhoneira Couraçada Nr.

Rio de Janeiro hit two mines on 2 September and rapidly sank, taking 53 of her crew with her.

Rio de Janeiro was designed to meet the need of the Brazilian Navy for a small, simple, shallow-draft armored gunboat capable of withstanding heavy fire.

A casemate ironclad design was chosen for ease of construction and a bronze ram, 1.8 meters (5 ft 11 in) long, was fitted.

The engine produced a total of 420 indicated horsepower (310 kW) which gave the ship a maximum speed of 9 knots (17 km/h; 10 mph).

[1] Rio de Janeiro mounted two 70-pounder Whitworth rifled muzzle loaders and two 68-pounder smoothbore guns in her casemate.

On 1 September Rio de Janeiro bombarded the Paraguayan fortifications at Curuzú in company with the other Brazilian ironclads.

The next day, after her damage was repaired, the ship struck two floating mines ('torpedoes') in the River Paraguay while trying to rendezvous with the other Brazilian ironclads bombarding Curupayty.