Townsend is a town in Middlesex County, Massachusetts, United States. The population was 8,927 at the 2010 census.
Townsend was first settled by Europeans in 1676, and was officially incorporated in 1732. The town was named after Charles Townshend, English secretary of state and an opponent of the Tories. The town initially used the same spelling as its namesake, but the "h" was dropped c. 1780.
According to the United States Census Bureau, the town has a total area of 33.1 square miles (85.8 km2), of which 32.9 square miles (85.1 km2) is land and 0.2 square mile (0.6 km2) (0.72%) is water. Townsend has the largest land area of any town in Middlesex County.
Townsend is bordered by Mason, New Hampshire and Brookline, New Hampshire to the north, Pepperell to the east, Groton and Shirley to the southeast, Lunenburg to the south, and Ashby to the west.
Route 119 runs east-west through Townsend, and Route 13 runs north-south.
As of the census of 2010, there were 8,926 people, 3,240 households, and 2,483 families residing in the town.