Folsom is a census-designated place (CDP) in Delaware County, Pennsylvania, United States. It is part of Ridley Township. The population was 8,323 at the 2010 census.
Folsom is located in northern Ridley Township at 39°53′31″N 75°19′34″W (39.891978, -75.326231). It is bordered to the northwest by the borough of Swarthmore, to the north by Springfield Township and the borough of Rutledge, to the east by Pennsylvania Route 420, to the southeast by the borough of Prospect Park, to the south by the borough of Ridley Park, and to the southwest by Woodlyn in Ridley Township. Folsom is 11 miles (18 km) southwest of Center City, Philadelphia.
According to the United States Census Bureau, the Folsom CDP has a total area of 1.2 square miles (3.2 km2), all of it land.
As of the census of 2000, there were 8,072 people, 3,162 households, and 2,203 families residing in the CDP. The population density was 6,455.1 people per square mile (2,493.3/km2). There were 3,235 housing units at an average density of 2,587.0/sq mi (999.2/km2). The racial makeup of the CDP was 96.51% White, 1.83% African American, 0.01% Native American, 1.07% Asian, 0.11% from other races, and 0.47% from two or more races. Hispanic or Latino of any race were 0.59% of the population.
There were 3,162 households, out of which 28.6% had children under the age of 18 living with them, 56.6% were married couples living together, 9.7% had a female householder with no husband present, and 30.3% were non-families.