Gainesville is a city in Ozark County, Missouri, United States. The population was 745 at the 2020 census. It is the county seat of Ozar…Gainesville is a city in Ozark County, Missouri, United States. The population was 745 at the 2020 census. It is the county seat of Ozark County. Gainesville was platted in 1841, taking its name from Gainesville, Georgia, the native home of a large share of the early settlers. Gainesville was designated county seat of Ozark County in 1857. A post office called Gainesville has been in operation since 1860.