Williamstown is a town in Orange County, Vermont, United States. The population was 3,389 at the 2010 census, making it the second largest municipality in the county.
According to the United States Census Bureau, the town has a total area of 40.3 square miles (104.5 km2), of which 40.2 square miles (104.1 km2) is land and 0.2 square mile (0.4 km2) (0.40%) is water.
The Ainsworth State Park is a 905-acre (3.7 km2) park located in Williamstown which provides camping, hiking, and hunting.
As of the census of 2000, there were 3,225 people, 1,248 households, and 889 families residing in the town. The population density was 80.3 people per square mile (31.0/km2). There were 1,318 housing units at an average density of 32.8 per square mile (12.7/km2). The racial makeup of the town was 98.33% White, 0.06% African American, 0.28% Native American, 0.12% Asian, 0.25% from other races, and 0.96% from two or more races. Hispanic or Latino of any race were 0.78% of the population.
There were 1,248 households out of which 34.1% had children under the age of 18 living with them, 58.7% were married couples living together, 8.4% had a female householder with no husband present, and 28.7% were non-families.