Barangay San Mariano Norte

Classified as a very small barangay, Barangay San Mariano Norte is one of the administrative divisions of San Guillermo in Isabela, Cagayan Valley, Philippines.

According to the 2020 Philippine census, Barangay San Mariano Norte had a population of 266. This made it the 25th largest of 26 barangays in San Guillermo by population, placing it among the smaller barangays of the municipality. Residents of Barangay San Mariano Norte accounted for approximately 1.27% of the total population of San Guillermo, which stood at 20,915 in the same census year.

Between the 2015 and 2020 censuses, the population of Barangay San Mariano Norte changed from 249 to 266, a shift of +6.8% over the five-year period. This places the barangay among those with growing populations in San Guillermo. Barangay San Mariano Norte is officially classified as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

San Guillermo is a municipality comprising 26 barangays, and serves as the governing unit directly responsible for local services in Barangay San Mariano Norte, including public health, sanitation, peace and order, and civil registration. Within the wider province of Isabela, which contains 1,055 barangays across its component cities and municipalities, Barangay San Mariano Norte ranks 1036th by 2020 population. Isabela 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.