| Treaty of Triple Alliance celebrated the 1st of May 1865 between the Empire of Brazil, the Republic of Argentina and the Oriental Republic of Uruguay | |
|---|---|
 Allied troops recapturing Corrientes province, Argentina. Painting by Cándido López (1840–1902), who was there. | |
| Signed | 1 May 1865 |
| Location | Buenos Aires, Argentina |
| Effective | Variable according to Article XIX. Some immediate, some when ratified. |
| Signatories | |
| Languages | Spanish, Portuguese |
The Treaty of the Triple Alliance was a treaty that allied the Empire of Brazil, Argentina, and Uruguay against Paraguay. Signed in 1865, after the outbreak of the Paraguayan War, its articles (plus a Protocol) prescribed the allies' actions both during and after the war. The war led to the near-annihilation of Paraguay.
After the defeat of Paraguay in 1870, Brazil and Argentina, who were traditional enemies, hovered on the brink of mutual warfare for six years because of disputes and misunderstandings about the treaty.