The Battle of Curupayty is Paraguay's only significant victory in the Paraguayan War.

The Battle of Curupayty was a key battle in the Paraguayan War. On the morning on 22 September 1866, the joint force of Brazilian, Argentine, and Uruguayan armies attacked Paraguayan fortified trenches on Curupayty. The Paraguayans were led by general José Eduvigis Díaz. This position was held by 5,000 men and 49 cannons, some of them in hidden places out of the attackers view. The Imperial Brazilian Navy gave support to the 20,000 assailants, but the ships had to keep some distance from the guns at the fortress of Humaitá, which led to the lack of accuracy and impact of the ship's fire. The navy's failure was crucial at the later ground battle result.

The Paraguayan War, also known as the War of the Triple Alliance, was a South American war that lasted from 1864 to 1870. It was fought between Paraguay and the Triple Alliance of Argentina, the Empire of Brazil, and Uruguay. It was the deadliest and bloodiest inter-state war in Latin American history. Paraguay sustained large casualties, but even the approximate numbers are disputed. Paraguay was forced to cede disputed territory to Argentina and Brazil. The war began in late 1864, as a result of a conflict between Paraguay and Brazil caused by the Uruguayan War. Argentina and Uruguay entered the war against Paraguay in 1865, and it then became known as the "War of the Triple Alliance".