Clarksville is a city in Johnson County, Arkansas, United States. As of the 2020 census the population was 9,381, up from 9,178 in 2010. The city is the county seat of Johnson County. It is nestled between the Arkansas River and the foothills of the Ozark Mountains, and Interstate 40 and US Highway 64 intersect within the city limits. Clarksville-Johnson County is widely known for its peaches, scenic byways and abundance of natural outdoor recreational activities.