South Alamo is a census-designated place (CDP) in Hidalgo County, Texas, United States.

[4] According to the United States Census Bureau, the CDP has a total area of 2.0 square miles (5.2 km2), all land.

South Alamo first appeared as a census designated place in the 2000 U.S.

4.8% of all households were made up of individuals, and 1.8% had someone living alone who was 65 years of age or older.

South Alamo is in the Donna Independent School District.