Hennepin
- County:
- Putnam County
- County Seat:
- Yes
- Area (mi²):
- 5.307
- State:
- Illinois
Hennepin is a village located in Putnam County, Illinois. Hennepin has a 2026 population of 747. It is also the county seat of Putnam County. Hennepin is currently growing at a rate of 0.27% annually but its population has decreased by -1.58% since the most recent census, which recorded a population of 759 in 2020.