The Ecuadorian–Peruvian War, also known as the War of '41 (), was a border war fought from July 5–31, 1941. It was the first of three military conflicts that occurred between these two South American nations during the 20th century. A cease-fire agreement between the two countries went into effect on July 31, 1941. Both countries signed the Protocolo de Río de Janeiro on January 29, 1942, and Peruvian forces subsequently withdrew.