Barangay Mambug

Classified as a small barangay, Barangay Mambug is one of the administrative divisions of Santiago in Ilocos Sur, Ilocos Region, Philippines.

According to the 2020 Census of Population and Housing conducted by the Philippine Statistics Authority, Barangay Mambug had a population of 1,168. This made it the 5th largest of 24 barangays in Santiago by population, placing it in the upper half of the municipality. Residents of Barangay Mambug accounted for approximately 6.00% of the total population of Santiago, which stood at 19,471 in the same census year.

The barangay recorded 1,200 residents in the 2015 intercensal count and 1,168 residents in the 2020 Census — a net change of -2.7%, consistent with a contracting settlement. The Philippine Statistics Authority classifies Barangay Mambug as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

Santiago is a municipality comprising 24 barangays, and serves as the governing unit directly responsible for local services in Barangay Mambug, including public health, sanitation, peace and order, and civil registration. Within the wider province of Ilocos Sur, which contains 768 barangays across its component cities and municipalities, Barangay Mambug ranks 187th by 2020 population. Ilocos Sur is classified as a 1st by the Bureau of Local Government Finance, a category that reflects the province's annual regular income.

The barangay's legislative and executive affairs are handled by a Punong Barangay and the Sangguniang Barangay, elected nationwide during the Barangay and SK Elections. The next BSKE is scheduled for Monday, November 2, 2026, following the synchronized election schedule set by COMELEC Resolution No. 11191.