Osage is a city in Mitchell County, Iowa, United States. The population was 3,627 at the time of the 2020 census. It is the county seat of Mitchell County.

Mitchell County is a county located in the U.S. state of Iowa. As of the 2020 census, the population was 10,565. The county seat is Osage. It is not clear whom the county is named after: the county website mentions John Mitchell, an early surveyor, and an Irish patriot John Mitchel.