South Dennis is a census-designated place (CDP) in the town of Dennis in Barnstable County, Massachusetts, United States. The population was 3,643 at the 2010 census, the most of the 5 CDPs in Dennis.
South Dennis is located on Cape Cod in the center of the town of Dennis at 41°42′21″N 70°9′45″W. It is bordered by the town of Brewster to the northeast, the town of Harwich to the southeast, the CDPs of Dennis Port to the south and West Dennis to the southwest, the town of Yarmouth to the west, and the CDPs of Dennis and East Dennis to the north.
According to the United States Census Bureau, the South Dennis CDP has a total area of 4.7 square miles (12.3 km2). 4.6 square miles (11.8 km2) of it is land, and 0.19 square miles (0.5 km2) of it (4.19%) is water.
As of the census of 2000, there were 3,679 people, 1,681 households, and 1,059 families residing in the CDP. The population density was 312.2/km2 (808.3/mi2). There were 2,468 housing units at an average density of 209.4/km2 (542.3/mi2). The racial makeup of the CDP was 95.41% White, 1.01% African American, 0.60% Native American, 0.35% Asian, 0.90% from other races, and 1.74% from two or more races. Hispanic or Latino of any race were 1.30% of the population.
There were 1,681 households, out of which 23.7% had children under the age of 18 living with them, 48.7% were married couples living together, 10.9% had a female householder with no husband present, and 37.0% were non-families.