Basilan Island
The province encompasses Basilan Island and all nearby offshore islands, together with the Pilas Island group (now Hadji Muhtamad Municipality) west of the island, and the Bubuan and Tapiantana Island group (now Tabuan-Lasa Municipality) in the south. These are listed among the Philippine islands with a moderate risk of getting hit by tsunamis. The province has a land area of under its jurisdiction. Basilan Island itself has an area of and a shoreline of .