Fairfax County is in the Commonwealth of Virginia, in the United States, just outside Washington, D.C., as part of the Northern Virginia suburbs of the nation’s capital.

More specifically, it sits to the west and southwest of Washington, D.C., forming part of the Washington metropolitan area. The county seat is the independent City of Fairfax, which lies roughly in the geographic center of the county, about 14 miles (around 23 km) west of downtown Washington, D.C.