Cagayan Valley (Lambak ng Cagayan in Filipino) is a region of the Philippines, also designated as Region II or Region 02. It is composed of five provinces, namely: Batanes, Cagayan, Isabela, Nueva Vizcaya, and Quirino. Its regional center is Tuguegarao City.
Most of the region lies in a large valley in northeastern Luzon, between the Cordilleras and the Sierra Madre mountain ranges. Cagayan River, the country's longest river runs through its center and flows out to Luzon Strait in the north, in the town of Aparri, Cagayan. The Babuyan and Batanes island groups that lie in the Luzon Strait also belong to the region.
The Cagayan Valley Region is defined by the Cagayan River, the largest in the Philippines. The Province of Cagayan occupies the lower course of the river, and the northeast corner of the island of Luzon (with a few offshore islets). Cagayan's area is 9,003 sq.km., its population 952,000 (by the 2000 census) in twenty-nine towns, of which Tuguegarao is the capital.