The Battle of Itapirú took place during the Paraguayan War on April 17, 1866, after Brazil's capture of Purutué Bank a week earlier.

The battle marked the beginning of the Triple Alliance's invasion of Paraguay.

On April 16, the Itapirú [es] fort was heavily bombed by the Imperial Navy while 10,000 troops from the Imperial Army crossed the Paraná River, and the next day, the confrontation with 4,000 Paraguayans took place under the command of Lieutenant Colonel Benítez, resulting in their withdrawal to Itapirú.

Faced with the concentration of Brazilian troops that began the invasion of Paraguayan territory, Francisco Solano López ordered the fortification abandoned, allowing Brazilian troops to occupy it on April 18.

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