San Narciso is a coastal municipality in the province of Zambales.
The municipality has a land area of 71.60 square kilometers or 27.64 square miles which constitutes 1.97% of Zambales’s total area. Its population as determined by the 2020 Census was 30,759. This represented 4.73% of the total population of Zambales province, or 0.25% of the overall population of the Central Luzon region. Based on these figures, the population density is computed at 430 inhabitants per square kilometer or 1,113 inhabitants per square mile.