Ilagan, officially the City of Ilagan (Filipino: Lungsod ng Ilagan) (PSGC: 023114000), is a component city in the province of Isabela, Philippines. It is the provincial capital, the most populous city in the province, and with a total land area of 116,626 hectares (288,190 acres), the largest city in the island of Luzon and the fourth largest city (in terms of land area) in the Philippines, after Davao City, Puerto Princesa and Zamboanga City.