White Knoll is an unincorporated area and census-designated place in Lexington County, South Carolina, United States. It was first listed as a CDP in the 2020 census with a population of 7,858.The CDP is in central Lexington County, bordered to the north by Red Bank and 5 miles south of Lexington, the county seat. South Carolina Highway 6 passes through the community, leading north to Lexington and southeast 15 miles to Swansea.