Oxon Hill is an unincorporated area and census-designated place (CDP) in southern Prince George's County, Maryland, United States. Oxon Hill is a close suburb of Washington, located southeast of the downtown district and east of Alexandria, Virginia. In 2008, the 300-acre (120 ha) National Harbor development on the shore of the Potomac River opened in Oxon Hill; it has since become a CDP of its own.