Chiloé Island also known as Greater Island of Chiloé (Isla Grande de Chiloé), is the largest island of the Chiloé Archipelago off the west coast of Chile, in the Pacific Ocean. The island is located in southern Chile, in the Los Lagos Region.

Of roughly rectangular shape, the southwestern half of the island is a wilderness of contiguous forests and swamps. Mountains in the island form a belt running from the northwestern to the southeastern corner of the island. Cordillera del Piuchén make up the northern mountains and the more subdued Cordillera de Pirulil gathers the southern mountains. The landscape of the northeastern sectors of Chiloé Island is dominated by rolling hills with a mosaic of pastures, forests and cultivated fields. While the western shores are rocky and relatively straight, the eastern and northern shores contain many inlets, bays and peninsulas, and it is here where all towns and cities lie.

Geographically, the bulk of the island is a continuation of the Chilean Coast Range, with the sea of Chiloé being a submerged portion of the Chilean Central Valley. The climate is cool temperate oceanic with Mediterranean precipitation pattern.