The Battle of San Nicolás was a naval engagement on 2 March 1811 on the Paraná River between the Spanish royalists from Montevideo, and the first flotilla created by the revolutionary government of Buenos Aires.

On 25 May 1810 the River Plate colonies revolted against the Spanish Viceroy at the May Revolution in Buenos Aires, claiming the necessity of assuming local government due to the difficult situation in Spain, which was occupied by Napoleonic troops.

In the city of Montevideo, there was a navy base serving as port for the royal Spanish fleet in the South American Atlantic coast.

With effort, Gurruchaga bought five vessels of different types from local owners, and equipped three of them with artillery, which had been taken for the most part out of service as obsolete.

This sailor had arrived in the River Plate at the beginning of the 19th century, and had participated in the British invasions of the Río de la Plata of 1806 and 1807.

The Maltese raised his flag in the "Invencible", while the Frenchman naturalized Argentine Hipólito Bouchard was put in charge of the brigantine "25 de Mayo".

In the first encounter, two royalist brigantines ("Belén" and "Cisne") became groundned near the coast and were made targets for the coastal cannons and the rebel infantry.

The royalists then concentrated on the "25 de Mayo", which they tried to board; the poorly trained crew became panicked and abandoned ship jumping overboard, against the attempts of Bouchard to stop them.

Finally in 1820, the liberal movement in Spain headed by general Rafael de Riego freed all political prisoners including Azopardo allowing him to return to South America.