Ozark County is a county in the southern portion of the U.S. state of Missouri. As of the 2020 census, the population was 8,553. The largest city and county seat is Gainesville. The county was organized as Ozark County, named after the Ozark Mountains, on January 29, 1841. It was renamed Decatur County, after Commodore Stephen Decatur, from 1843 to 1845, after which the name Ozark County was restored.