Allendale is a town in Allendale County, South Carolina, United States. The population was 4,052 at the 2000 census. It is the county seat of Allendale County.
According to the United States Census Bureau, the town has a total area of 3.3 square miles (8.6 km²), all of it land.
As of the census of 2000, there were 4,052 people, 1,542 households, and 997 families residing in the town. The population density was 1,225.2 people per square mile (472.7/km²). There were 1,763 housing units at an average density of 533.1 per square mile (205.6/km²). The racial makeup of the town was 18.19% White, 80.03% African American, 0.17% Asian, 0.17% Pacific Islander, 0.96% from other races, and 0.47% from two or more races. Hispanic or Latino of any race were 2.25% of the population.