Mason City
- County:
- Cerro Gordo County
- County Seat:
- Yes
- Area (mi²):
- 28.289
- State:
- Iowa
Mason City is a city located in Cerro Gordo County, Iowa. Mason City has a 2026 population of 26,948. It is also the county seat of Cerro Gordo County. Mason City is currently declining at a rate of -0.02% annually and its population has decreased by -1.22% since the most recent census, which recorded a population of 27,280 in 2020.