Green Valley is a census-designated place (CDP) and unincorporated community in Pennington County, South Dakota, United States.

[2] According to the United States Census Bureau, the CDP has a total area of 3.7 square miles (9.6 km2), all land.

There were 321 housing units at an average density of 86.5 per square mile (33.4/km2).

The racial makeup of the CDP was 95.57% White, 2.73% Native American, 0.13% Asian, 0.13% Pacific Islander, and 1.43% from two or more races.

23.9% of all households were made up of individuals, and 4.8% had someone living alone who was 65 years of age or older.