Patagonia is a region located at the southern end of South America, territory shared by Argentina and Chile, which comprises the southern section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the mountain range to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean. To the west, it includes the territory of Valdivia through Tierra del Fuego archipelago.
The name Patagonia comes from the word patagón used by Magellan in 1520 to describe the native people that his expedition thought to be giants. It is now believed the Patagons were actually Tehuelches with an average height of 180 cm (~5′11″) compared to the 155 cm (~5′1″) average for Spaniards of the time.
The Argentine portion of Patagonia includes the provinces of Neuquén, Río Negro, Chubut and Santa Cruz, as well as the eastern portion of Tierra del Fuego archipelago and the southernmost department of Buenos Aires province: Patagones. The Argentine politico-economic Patagonic Region includes the Province of La Pampa.
The Chilean part of Patagonia embraces the southern provinces and regions of Aisén and Magallanes, including the west side of Tierra del Fuego and Cape Horn, and Palena Province in Los Lagos Region.
Information based on http://en.wikipedia.org/wiki/Patagonia