Chiloé Island also known as Greater Island of Chiloé, is the largest island of Chiloé Archipelago off the coast of Chile, in the Pacific Ocean. The island is located in southern Chile, in the Los Lagos Region. The variety of potato which is most widely grown throughout the world is indigenous to the island.
Chiloé Island is the second largest island in Chile (and the fifth largest in South America), after the Isla Grande de Tierra del Fuego. It is separated from the Chilean mainland by the Chacao Strait ("Canal Chacao") to the north, and by the Gulf of Ancud (Golfo de Ancud) and the Gulf of Corcovado (Golfo Corcovado) to the east; the Pacific ocean lies to the west, and the Chonos Archipelago lies to the south, across the Boca del Guafo. The island is 190 km from north to south, and averages 55–65 km wide. The capital is Castro, on the east side of the island; the second largest town is Ancud, at the island's northwest corner, and there are several smaller port towns on the east side of the island, such as Quellón, Dalcahue and Chonchi.
Chiloé Province includes all the Chiloé Archipelago except the Grupo Desertores islands, plus the Isla Guafo. The administrative center of the province is Castro, while the episcopal see of the Roman Catholic bishopric is Ancud. Chiloé province is part of the Los Lagos Region (Región de los Lagos), which mainly includes the Chilean lakes region on the mainland north of Chiloé. The administrative center of the region is Puerto Montt.
Chiloé and the Chonos Archipelago are a southern extension of the Chilean coastal range, which runs north and south, parallel to the Pacific coast and the Andes Mountains. The Chilean Central Valley lies between the coastal mountains and the Andes, of which the Gulfs of Ancud and Corcovado form the southern extension. Mountains run north and south along the spine of the island. The east coast is deeply indented, with several natural harbors and numerous smaller islands.