Chiloé Island is by far the largest island in the archipelago, at . It is roughly rectangular, with its long axis oriented from north to south. To the east of Chiloé Island lies the Sea of Chiloé, which contains most of the other islands in the archipelago. The Sea of Chiloé is a marginal sea separating Chiloé Island from Palena Province (also called Continental Chiloé). The main islands in the Sea of Chiloé are Quinchao, Lemuy, Tranqui, and Desertores Islands. To the northeast and southeast of the archipelago lie the Gulf of Ancud and the Gulf of Corcovado; the former is part of the Sea of Chiloé. Some southwest of Chiloé Island lies Guafo Island, the southernmost island of the archipelago.