An earthquake occurred in the Argentine province of Mendoza, causing at least 6,000 deaths and destroying most of the buildings in the province's capital city.

The 1861 Mendoza earthquake occurred in the province of Mendoza, Argentina on 20 March at 11:30 PM. It had an estimated magnitude of 7.2 on the M_s scale and an intensity of IX–X on the Mercalli scale. Its hypocenter was located at an estimated depth of 30 kilometres (19 mi).

Mendoza, officially the Province of Mendoza, is a province of Argentina, in the western central part of the country in the Cuyo region. It borders San Juan to the north, La Pampa and Neuquén to the south, San Luis to the east, and the republic of Chile to the west; the international limit is marked by the Andes mountain range. Its capital city is the homonymous city of Mendoza.

Mendoza, officially the City of Mendoza, is the capital of the province of Mendoza in Argentina. It is located in the northern-central part of the province, in a region of foothills and high plains, on the eastern side of the Andes. As of the 2010 census [INDEC], Mendoza had a population of 115,041 with a metropolitan population of 1,055,679, making Greater Mendoza the fourth largest census metropolitan area in the country.