Fairfax County, officially the
County of Fairfax, is a
county in the
Commonwealth of
Virginia. As of the
2010 census, the population was 1,081,726, in 2014, the population was estimated to be 1,118,883, making it the most populous jurisdiction in the Commonwealth of Virginia, with 13.6% of Virginia's population. The county is also the most populous jurisdiction in the
Washington-Arlington-Alexandria, DC-VA-MD-WV Metropolitan Statistical Area, with 19.8% of the
MSA population, as well as the larger Washington-Baltimore-Arlington, DC-MD-VA-WV-PA Combined Statistical Area, with 13.1% of the
CSA population. The
county seat is
Fairfax.