Patagonia is a geographic region containing the southernmost portion of South America. Mostly located in Argentina and partly in Chile, it comprises the Andes mountains to the west and south, and plateaux and low plains to the east. The name Patagonia comes from the word patagon Antonio Pigafetta, Relazione del primo viaggio intorno al mondo, 1524: "Il capitano generale nominò questi popoli Patagoni." The original word would probably be in Magellan's native Portuguese (patagão) or the Spanish of his men (patagón). It has been interpreted later as "big foot" but the etymology is unclear. used by Magellan to describe the native people who his expedition thought to be giants. It is now believed the Patagons were actually Tehuelches and Aonikenk with an average height of 1.80 m (~5'11") compared to the 1.55 m (~5'1") average for Spaniards of the time.

To the east of the Andes, it lies south of the Neuquén River and Colorado rivers, and, to the west of the Andes, south of (39°S), excluding the Chiloé Archipelago. Patagonia: Natural History, Prehistory and Ethnography at the Uttermost End of the Earth, C. McEwan, L.A. Borrero and A. Prieto (eds), Princeton University Press with British Museum Press, 1997. ISBN 0-691-05849-0 East of the Andes the Argentine portion of Patagonia includes the provinces of Neuquén, Río Negro, Chubut, Santa Cruz, and Tierra del Fuego, as well as the southern tips of the provinces of Buenos Aires, Mendoza and La Pampa. The Chilean portion embraces the southern part of the region of Los Lagos, and the regions of Aisén and Magallanes. It excludes those portions of Antarctica claimed by both countries.