South Valley Stream is an unincorporated hamlet and census-designated place (CDP) in the Town of Hempstead in Nassau County, on Long Island, in New York, United States.

South Valley Stream is located in the southern part of the Town of Hempstead, and consists of two unincorporated areas, North Woodmere and Mill Brook.

According to the United States Census Bureau, the CDP has a total area of 0.9 square miles (2.3 km2), all land.

[3] The Green Acres Mall is located along the border of the hamlet and the Village of Valley Stream.

There were 2,045 housing units at an average density of 2,326.9 per square mile (898.4/km2).