Barangay Old San Agustin

Barangay Old San Agustin forms part of Basey, a municipality in Samar, and is classified as a small barangay.

According to the 2020 Census of Population and Housing conducted by the Philippine Statistics Authority, Barangay Old San Agustin had a population of 1,810. This made it the 6th largest of 51 barangays in Basey by population, placing it among the most populous barangays of the municipality. Residents of Barangay Old San Agustin accounted for approximately 3.19% of the total population of Basey, which stood at 56,685 in the same census year.

The barangay recorded 1,812 residents in the 2015 intercensal count and 1,810 residents in the 2020 Census — a net change of -0.1%, consistent with a broadly stable settlement. The Philippine Statistics Authority classifies Barangay Old San Agustin as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

Basey is a municipality comprising 51 barangays, and serves as the governing unit directly responsible for local services in Barangay Old San Agustin, including public health, sanitation, peace and order, and civil registration. Within the wider province of Samar, which contains 951 barangays across its component cities and municipalities, Barangay Old San Agustin ranks 84th by 2020 population. Samar 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.