Barangay San Isidro Zone I (Pob.)

Barangay San Isidro Zone I (Pob.) forms part of City of Tayabas, a city in Quezon, and is classified as a small barangay.

According to the 2020 Philippine census, Barangay San Isidro Zone I (Pob.) had a population of 575. This made it the 43rd largest of 66 barangays in City of Tayabas by population, placing it in the middle tier of the city. Residents of Barangay San Isidro Zone I (Pob.) accounted for approximately 0.51% of the total population of City of Tayabas, which stood at 112,658 in the same census year.

The barangay recorded 616 residents in the 2015 intercensal count and 575 residents in the 2020 Census — a net change of -6.7%, consistent with a contracting settlement. Barangay San Isidro Zone I (Pob.) is officially classified as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

City of Tayabas is a city comprising 66 barangays, and serves as the governing unit directly responsible for local services in Barangay San Isidro Zone I (Pob.), including public health, sanitation, peace and order, and civil registration. Within the wider province of Quezon, which contains 1,242 barangays across its component cities and municipalities, Barangay San Isidro Zone I (Pob.) ranks 876th by 2020 population. Quezon 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.