St. Peter
- County:
- Fayette County
- County Seat:
- No
- Area (mi²):
- 0.521
- State:
- Illinois
St. Peter is a village located in Fayette County, Illinois. St. Peter has a 2026 population of 312. St. Peter is currently declining at a rate of -0.32% annually and its population has decreased by -2.5% since the most recent census, which recorded a population of 320 in 2020.
The median household income in St. Peter is $63,500 with a poverty rate of 10.36%. The median age in St. Peter is 39.7 years: 35.8 years for males, and 45.3 years for females. For every 100 females there are 109.9 males.