Springfield
- County:
- Sangamon County
- County Seat:
- Yes
- Area (mi²):
- 61.261
- State:
- Illinois
Springfield is a city located in Sangamon County, Illinois. Springfield has a 2026 population of 112,949. It is also the county seat of Sangamon County. Springfield is currently declining at a rate of -0.05% annually and its population has decreased by -1.25% since the most recent census, which recorded a population of 114,375 in 2020.