Fort Pierce South is a census-designated place (CDP) in St. Lucie County, Florida, United States.

It is part of the Port St. Lucie Metropolitan Statistical Area.

[3] According to the United States Census Bureau, the CDP has a total area of 4.5 square miles (12 km2), all land.

There were 2,213 housing units at an average density of 491.4 per square mile (189.7/km2).

20.8% of all households were made up of individuals, and 7.8% had someone living alone who was 65 years of age or older.