Harrison Manley (d. 1773), was the son of John Manley (d. 1750) and Sarah Harrison Manley, and the brother of Penelope Manley French. Manley occasionally sold wheat to GW and used the services of GW's mill, blacksmith shop, and weaving shop as part payment in return. In Fairfax County Manley owned a small tract of land on the southwestern part of Mount Vernon Neck which GW was finally able to purchase in 1786. This tract, along with a larger one he was to acquire the same year from Penelope French, would complete GW's acquisition of the entire neck of land originally granted in the seventeenth century to Nicholas Spencer and John Washington.

Harrison Manley was married to Margaret Manley who remarried after his death in 1773. They had at least one child, Mary (Molly) Manley.