San Martín, José de (1778-1850), South American revolutionary, one of the principal leaders of the independence movement. 

San Martín was born on February 25, 1778, in Yapeyú, in the viceroyalty of La Plata (now in Argentina). He lived for most of his early life in Spain, where he served as an officer in the Spanish army. Sympathizing with the efforts of Spain's American colonies to win their freedom, he returned to Argentina in 1812 and began to train a revolutionary army to aid the struggle for independence. In 1817 he led a rebel force across the Andes Mountains, defeated the Spanish at Chacabuco, Chile, and occupied the Chilean capital, Santiago. In 1818, following his decisive victory at Maipu, he established a nationalist government in Chile but refused the presidency in favor of his lieutenant, the Chilean general

In 1820 San Martín organized an expedition to liberate Peru from Spanish rule. He defeated the Spanish army at Pisco in December 1820, and then occupied Lima, where, on July 28, 1821, he proclaimed the independence of Peru and was appointed protector of the country. The next year further Spanish resistance forced him to request military aid of the Venezeulan general and liberator Símon Bolívar. The two men disagreed on governmental policy and in September 1822, San Martín resigned his position in favor of Bolívar. In 1824 San Martín went to Europe, where he remained until his death in Boulogne, France, on August 17, 1850.