Green Grass
- County:
- Dewey County
- County Seat:
- No
- Area (mi²):
- 8.133
- State:
- South Dakota
Green Grass is a CDP located in Dewey County, South Dakota. Green Grass has a 2025 population of 22. Green Grass is currently declining at a rate of 0% annually and its population has decreased by since the most recent census, which recorded a population of 22 in 2020.
The median age in Green Grass is 21 years: 22.6 years for males, and 18.7 years for females.