South Ashburnham is a census-designated place (CDP) in the town of Ashburnham in Worcester County, Massachusetts, United States.

[2] According to the United States Census Bureau, the CDP has a total area of 7.8 km2 (3.0 mi2), of which 7.8 km2 (3.0 mi2) is land and 0.33% is water.

At the 2000 census there were 1,013 people, 365 households, and 286 families living in the CDP.

Of the 365 households 37.5% had children under the age of 18 living with them, 60.5% were married couples living together, 12.9% had a female householder with no husband present, and 21.6% were non-families.

Males had a median income of $35,139 versus $31,250 for females.