The Crossing of the Andes (Spanish: Cruce de los Andes) was one of the most important feats in the Argentine and Chilean wars of independence, in which a combined army of Argentine soldiers and Chilean exiles invaded Chile crossing the Andes range separating Argentina from Chile, leading to Chile's liberation from Spanish rule.

Led by Jos de San Martn, and setting out from Mendoza then part of the Province of Cuyo, Argentina in January 1817, the successful crossing of the army took 21 days. Having to manage heights averaging 3,000 mts, the feat has been compared to Hannibal's or Napoleon's crossing of the Alps, and is regarded among the greatest of its kind in universal military history

José Francisco de San Martín y Matorras (25 February 1778 – 17 August 1850), known simply as José de San Martín (Spanish pronunciation: [xoˈse ðe san maɾˈtin] (listen)) or the Liberator of Argentina, Chile and Peru, was an Argentine general and the primary leader of the southern and central parts of South America's successful struggle for independence from the Spanish Empire who served as the Protector of Peru. Born in Yapeyú, Corrientes, in modern-day Argentina, he left the Viceroyalty of the Río de la Plata at the early age of seven to study in Málaga, Spain.

In 1808, after taking part in the Peninsular War against France, San Martín contacted in London South American supporters of independence from Spain. In 1812, he set sail for Buenos Aires and offered his services to the United Provinces of the Río de la Plata, present-day Argentina. After the Battle of San Lorenzo and time commanding the Army of the North during 1814, he organized a plan to defeat the Spanish forces that menaced the United Provinces from the north, using an alternative path to the Viceroyalty of Peru. This objective first involved the establishment of a new army, the Army of the Andes, in Cuyo Province, Argentina. From there, he led the Crossing of the Andes to Chile, and triumphed at the Battle of Chacabuco and the Battle of Maipú (1818), thus liberating Chile from royalist rule. Then he sailed to attack the Spanish stronghold of Lima, Peru.

On 12 July 1821, after seizing partial control of Lima, San Martín was appointed Protector of Peru, and Peruvian independence was officially declared on 28 July. On 26 July 1822, after a closed-door meeting with fellow libertador Simón Bolívar at Guayaquil, Ecuador, Bolívar took over the task of fully liberating Peru. San Martín unexpectedly left the country and resigned the command of his army, excluding himself from politics and the military, and moved to France in 1824. The details of that meeting would be a subject of debate by later historians.

San Martín is regarded as a national hero of Argentina, Chile and Peru, a great military commander, and one of the Liberators of Spanish South America. The Order of the Liberator General San Martín (Orden del Libertador General San Martín), created in his honor, is the highest decoration conferred by the Argentine government.