St. Louis
- County:
- Gratiot County
- County Seat:
- No
- Area (mi²):
- 3.315
- State:
- Michigan
St. Louis is a city located in Gratiot County, Michigan. St. Louis has a 2026 population of 7,465. St. Louis is currently declining at a rate of -0.15% annually but its population has increased by 0.13% since the most recent census, which recorded a population of 7,455 in 2020.