Clarksville is a city in Montgomery County, Tennessee, USA. Clarksville is the county seat of Montgomery County and is Tennessee's fifth largest city. As of the 2010 census , the city had a total population of 132,929, and as of 2017 had an estimated population of 153,205. Clarksville is the central city of the Clarksville-Hopkinsville metropolitan statistical area, which is made up of Montgomery County, Tennessee, and Christian County, Kentucky.