Agar
- County:
- Sully County
- County Seat:
- No
- Area (mi²):
- 0.205
- State:
- South Dakota
Agar is a town located in Sully County, South Dakota. Agar has a 2026 population of 68. Agar is currently declining at a rate of 0% annually and its population has increased by 4.62% since the most recent census, which recorded a population of 65 in 2020.