Caraballo Mountains in the context of Sierra Madre (Philippines)

Cagayan Valley (Ilocano: Tanap ti Cagayan; Filipino: Lambak ng Cagayan; Spanish: Valle del Cagayán), designated as Region II, is an administrative region in the Philippines. Located in the northeastern section of Luzon, it is composed of five Philippine provinces: Batanes, Cagayan, Isabela, Nueva Vizcaya, and Quirino. The region hosts four chartered cities: Cauayan, Ilagan, Santiago, and Tuguegarao (the regional center and largest city).

Most of its land area lies in the valley between the Cordilleras and the Sierra Madre mountain ranges. The eponymous Cagayan River, the country's largest and longest, runs through the region, flows from the Caraballo Mountains, and ends in Aparri. Cagayan Valley is the second-largest Philippine administrative region by land area. According to a literacy survey in 2019, 93% of Cagayan Valley's citizens (ages 10 to 64) are functionally literate, which is 5th out of the 17 regions of the Philippines.

The Cordillera Central or Cordillera Range is a massive mountain range 320 kilometres (200 mi) long north–south and 118 kilometres (73 mi) east-west situated in the north-central part of the island of Luzon, in the Philippines. The mountain range encompasses all provinces of the Cordillera Administrative Region (Abra, Apayao, Benguet, Ifugao, Kalinga and Mountain Province), as well as portions of eastern Ilocos Norte, eastern Ilocos Sur, eastern La Union, northeastern Pangasinan, western Nueva Vizcaya, and western Cagayan.

To the north, the mountain range terminates at the northern shores of Luzon along the Babuyan Channel in Ilocos Norte and Cagayan provinces. At its southeastern part, the Central Cordillera is linked to the Sierra Madre Mountains, the longest mountain range in the country, through the Caraballo Mountains in Nueva Vizcaya province. During Spanish colonial period, the whole range was called Nueva Provincia (New Province).