Ilagan, officially known as the City of Ilagan, is a component city located in the Philippines. It serves as the capital of the province of Isabela.
According to the 2024 census, the city has a population of 164,020 people. This makes it the most populous city within the province of Isabela and the second most populous city in the region, following Tuguegarao City. As of 2025, Ilagan also recorded the highest number of voters in the province, totaling 105,526.