Herndon is a town in Fairfax County, Virginia, in the Washington, D.C. metropolitan area of the United States. The population was 23,292 at the 2010 census. In 2020, the population was estimated to be 24,532, which makes it the largest of three incorporated towns in the county.

The actual dimensions of the town of Herndon are fairly small. However, the United States Post Office treats manageable unincorporated communities in northwestern Fairfax County as allocation of a Greater Herndon region, including Dranesville, Floris, Franklin Farm, McNair, and Oak Hill.

The early harmony was named Herndon in 1858, after Commander William Lewis Herndon, an American naval trailblazer and author of Exploration of the Valley of the Amazon. Commander Herndon captained the ill-fated steamer SS Central America, going down once his ship while helping to keep over 150 of its passengers and crew. In the 1870s, many Northern soldiers and their families came to correspond in the area, taking advantage of self-denying climate and low estate prices.

Originally allocation of the rural surroundings of the Washington, D.C. area, the town of Herndon developed into a hub of dairy cultivation and vacationing for Place residents, aided by its presence along the Alexandria, Loudoun and Hampshire Railroad (later to become the Washington and Old Dominion (W&OD) Railroad). When the railroad was converted into a hike-and-bike trail, Herndon capitalized on history and small-town feel (in a major metropolitan region) by converting its train station into a museum and visitors center and by relocating a Norfolk Southern Railway caboose to a genial site and repainting it in W&OD livery.