Surprise Valley township
- County:
- Mellette County
- County Seat:
- No
- Area (mi²):
- 33.505
- State:
- South Dakota
Surprise Valley township is located in Mellette County, South Dakota. Surprise Valley township has a 2025 population of 11. Surprise Valley township is currently declining at a rate of -8.33% annually and its population has decreased by -21.43% since the most recent census, which recorded a population of 14 in 2020.
The median age in Surprise Valley township is 72.2 years: 0 years for males, and 0 years for females.