Barangay Siain

Situated in Buenavista, Quezon, Barangay Siain is one of 37 barangays that make up the municipality within CALABARZON.

According to the 2020 Census of Population and Housing conducted by the Philippine Statistics Authority, Barangay Siain had a population of 422. This made it the 32nd largest of 37 barangays in Buenavista by population, placing it among the smaller barangays of the municipality. Residents of Barangay Siain accounted for approximately 1.35% of the total population of Buenavista, which stood at 31,160 in the same census year.

The barangay recorded 393 residents in the 2015 intercensal count and 422 residents in the 2020 Census — a net change of +7.4%, consistent with a growing settlement. The Philippine Statistics Authority classifies Barangay Siain as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

Buenavista is a municipality comprising 37 barangays, and serves as the governing unit directly responsible for local services in Barangay Siain, 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 Siain ranks 997th 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.

Barangay Siain is governed by an elected Sangguniang Barangay composed of a Punong Barangay and seven kagawads, with the Sangguniang Kabataan representing the youth. The next BSKE, set for Monday, November 2, 2026, will elect officials to four-year terms as provided under Republic Act No. 12232.