Annandale is a census-designated place (CDP) in Fairfax County, Virginia, United States. The population was 41,008 at the 2010 census, down from 54,994 in 2000 due to the splitting off of the western part of it to form Wakefield and Woodburn CDP's.
Annandale is located at 38°50′3″N 77°12′41″W / 38.83417°N 77.21139°W / 38.83417; -77.21139 (38.834134, -77.211277). Annandale is mostly traversed by the Capital Beltway and Virginia State Route 236. The center of town is considered to be where Route 236, Columbia Pike, and Backlick Road meet around two miles (3 km) east of Interstate 495 on Route 236.
According to the United States Census Bureau, the CDP has a total area of 13.8 square miles (36 km2), of which, 13.8 square miles (36 km2) of it is land and 0.17% is water. The area is part of the coastal plain located just east of the Fall Line separating the coastal plain of Virginia from the piedmont. It is characterized by rolling hills, stream valleys, and heavy red clay soils.