Williamstown is a borough in Dauphin County, Pennsylvania, United States. The borough is 38 miles (61 km) northeast of Harrisburg. Formerly, anthracite coal mines and hosiery mills were located in the borough. The population was 1,303 at the 2020 census.

The Harrisburg–Carlisle metropolitan statistical area, officially the Harrisburg–Carlisle, PA Metropolitan Statistical Area, and also referred to as the Susquehanna Valley, is defined by the Office of Management and Budget as an area consisting of three counties in South Central Pennsylvania, anchored by the cities of Harrisburg and Carlisle.