Barangay Lioac Sur

Classified as a small barangay, Barangay Lioac Sur is one of the administrative divisions of Naguilian in La Union, Ilocos Region, Philippines.

According to the 2020 Philippine census, Barangay Lioac Sur had a population of 1,291. This made it the 16th largest of 37 barangays in Naguilian by population, placing it in the middle tier of the municipality. Residents of Barangay Lioac Sur accounted for approximately 2.47% of the total population of Naguilian, which stood at 52,189 in the same census year.

The barangay recorded 1,434 residents in the 2015 intercensal count and 1,291 residents in the 2020 Census — a net change of -10.0%, consistent with a contracting settlement. Barangay Lioac Sur is officially classified as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

Naguilian is a municipality comprising 37 barangays, and serves as the governing unit directly responsible for local services in Barangay Lioac Sur, including public health, sanitation, peace and order, and civil registration. Within the wider province of La Union, which contains 576 barangays across its component cities and municipalities, Barangay Lioac Sur ranks 251st by 2020 population. La Union is classified as a 1st by the Bureau of Local Government Finance, a category that reflects the province's annual regular income.

Like every Philippine barangay, Barangay Lioac Sur is led by an elected Punong Barangay (barangay captain) supported by seven Sangguniang Barangay members (kagawads), an SK Chairperson, a Barangay Secretary, and a Barangay Treasurer. The next Barangay and Sangguniang Kabataan Elections (BSKE) are scheduled for Monday, November 2, 2026, with officials serving four-year terms under Republic Act No. 12232.