Charlton is a town in Hampden County, Massachusetts, United States. The population was 3,609 at the 2010 census. It is part of the Springfield, Massachusetts Metropolitan Statistical Area.
According to the United States Census Bureau, the town has a total area of 35.2 square miles (91 km2), of which, 34.7 square miles (90 km2) of it is land and 0.5 square miles (1.3 km2) of it (1.45%) is water. Charlton is located in Western Massachusetts. Charlton is bordered by Sturbridge on the east, Holland and Wales on the south, Monson and Palmer on the west, and Warren on the north. U.S. Route 20 and Route 19 both run through Charlton. Interstate 90 cuts through the northern portion of the town in two sections.