Zamboanga Peninsula (Zamboangueño: Peninsula de Zamboanga; Cebuano: Lawis sa Zamboanga) is an administrative region in the Philippines, designated as Region IX. The region consists of three provinces (Zamboanga del Norte, Zamboanga Sibugay and Zamboanga del Sur) and two independent cities (Isabela City and Zamboanga City). The region was previously known as Western Mindanao before the enactment of Executive Order No. 36 on September 19, 2001. The city of Pagadian is designated as the regional center.
The region is located on the eponymous Zamboanga Peninsula of the island of Mindanao, that lies between the Moro Gulf (part of the Celebes Sea) and the Sulu Sea. Along the shores of the peninsula are numerous bays and islands. The peninsula is connected to the rest of Mindanao through an isthmus situated between Panguil Bay and Pagadian Bay. Its territory consists of the three Zamboanga provinces and the city of Zamboanga, and the boundary between the peninsula and mainland is artificially marked by the border between the provinces of Zamboanga del Sur and Lanao del Norte.
However, operational jurisdiction or accomplishment of PDEA Regional Office IX includes the three provinces of ARMM (Basilan, Sulu and Tawi-Tawi).