Santa Inés Island (Spanish: Isla Santa Inés) is an island in southern Chile, part of the Tierra del Fuego archipelago and of Punta Arenas municipality, lying south west of the Brunswick Peninsula, from which is separated by the Strait of Magellan and minor islands. It is the largest island of Punta Arenas municipality and the third largest of the Tierra del Fuego archipelago, after Isla Grande and Hoste Island. Its shoreline in this area is part of the Francisco Coloane Coastal and Marine Protected Area. The rest of the island is a part of the Alacalufes National Reserve, equalling that Desolación Island and the Córdova Peninsula. This latter is located in front of the island on the other side of the Strait of Magellan and is a peninsula of Riesco Island. The island belongs to the Tierra del Fuego archipelago.