Dupo
- County:
- St. Clair County
- County Seat:
- No
- Area (mi²):
- 6.403
- State:
- Illinois
Dupo is a village located in St. Clair County, Illinois. Dupo has a 2026 population of 3,797. Dupo is currently declining at a rate of -0.84% annually and its population has decreased by -4.5% since the most recent census, which recorded a population of 3,976 in 2020.