Grantsville is a town in Calhoun County, West Virginia, in the United States. The population was 561 at the 2010 census. It is the county seat of Calhoun County. The town was established along the Little Kanawha River in 1865 and named for Ulysses S. Grant. Grantsville is home to Wayne Underwood Park, which includes a .25-mile-long (0.40 km) walking trail, and to the annual West Virginia Wood Festival.
Grantsville is located at 38°55′23″N 81°5′42″W (38.922921, -81.094920).
According to the United States Census Bureau, the town has a total area of 0.47 square miles (1.22 km2), of which, 0.44 square miles (1.14 km2) is land and 0.03 square miles (0.08 km2) is water.
As of the census of 2010, there were 561 people, 262 households, and 140 families living in the town. The population density was 1,275.0 inhabitants per square mile (492.3/km2). There were 303 housing units at an average density of 688.6 per square mile (265.9/km2). The racial makeup of the town was 98.9% White, 0.2% African American, 0.4% Native American, 0.4% Asian, and 0.2% from two or more races. Hispanic or Latino of any race were 0.2% of the population.