St. Marys
- County:
- Warren County
- County Seat:
- No
- Area (mi²):
- 0.141
- State:
- Iowa
St. Marys is a city located in Warren County, Iowa. St. Marys has a 2026 population of 116. St. Marys is currently growing at a rate of 2.65% annually and its population has increased by 0.87% since the most recent census, which recorded a population of 115 in 2020.
The median household income in St. Marys is $77,500 with a poverty rate of 8.33%. The median age in St. Marys is 55.5 years: 53.7 years for males, and 57.5 years for females. For every 100 females there are 118.2 males.