Lillington is a town in Harnett County, North Carolina, United States. The population was 3,194 at the 2010 census, and was estimated in 2016 to be 3,581. It is the county seat of Harnett County. Lillington is a part of the Dunn Micropolitan Area, which is also a part of the greater Raleigh?Durham?Cary Combined Statistical Area as defined by the United States Census Bureau.