Oak Hill is located in Fairfax County, just east of Washington Dulles International Airport and south of the Dulles Toll and Access Roads. The town of Herndon lies immediately to the north, while the unincorporated community of Chantilly is adjacent to Oak Hill in the south. Franklin Farm, Floris and McNair are census-designated places located within the larger Oak Hill community.
As an unincorporated area, Oak Hill’s boundaries are not officially defined by either a municipal government, the government of Fairfax County, or the U.S. Census Bureau. The United States Postal Service defines Oak Hill’s boundaries by way of its ZIP code, 20171.
Schools serving the Oak Hill area (but not necessarily in Oak Hill), include Oak Hill Elementary, Fox Mill Elementary, Floris Elementary, McNair Elementary, Lutie Lewis Coates Elementary, Navy Elementary, Crossfield Elementary, Franklin Middle School, Rachel Carson Middle School, Chantilly High School, South Lakes High School, Westfield High School, and Oakton High School.
The Oak Hill community is served by the Oak Hill post office. Mail may be addressed to Herndon or Oak Hill using zip code 20171.