Leesville is a city in, and the parish seat of, Vernon Parish, Louisiana, United States. The population was 6,612 at the 2010 United States Census. It is part of the Fort Polk South Micropolitan Statistical Area and is additionally served by the Leesville Airport. The city is home to the Fort Polk U.S. Army installation. The populations of Fort Polk and Leesville, if combined, would result in a city with a population of more than 20,000.