Places of Virginia

The geography and history of the Commonwealth

Fairfax County, Virginia

Quick answer: Fairfax County is a county in Virginia with its seat at Fairfax. Its estimated population in 2025 was 1,167,873, up 1.5% since 2020. It covers about 391 square miles of land.
Typecounty
County seatFairfax
Established1742
Population, 2025 estimate1,167,873
Population, 2020 estimate1,148,598
Change 2020–20251.7%
Rank by population in Virginia1 of 133
Church of the Apostles Fairfax Virginia
Photo: Dclemens1971 · CC BY 4.0 (license), via Wikimedia Commons, resized

Overview

Virginia has 95 counties, and Fairfax County is one of them.[1] The county seat is Fairfax.[2] The county was established in 1742.[2] The name comes from Thomas Fairfax.[2]

Population of Fairfax County

The U.S. Census Bureau estimated the population of Fairfax County at 1,167,873 in July 2025, up 1.5% from the April 2020 base of 1,150,294.[1] That made it 1st of Virginia's 133 counties and independent cities by population. It ranked 69th for growth since 2020.[1]

From 2020 to 2025 the Census Bureau counted about 64,491 births and 31,446 deaths, a natural increase of 33,045.[1] More people moved away to other parts of the United States than moved in. Net domestic migration was -73,778. Moves from abroad added 57,658.[1]

Geography

Fairfax County covers 391.0 square miles of land and 15.4 square miles of water.[3] By land area it ranks 47th of 133 in Virginia.[3] It had about 2,987 people per square mile in 2025, so it is one of the more densely settled places in the state. Its geographic center lies near 38.83° N, 77.27° W.[3]

The county borders the City of Alexandria, Arlington County, the City of Fairfax, the City of Falls Church, Loudoun County and Prince William County in Virginia, as well as land in Maryland.[4]

The U.S. Geological Survey place-name database lists 92 named streams, 7 named summits, 31 lakes and reservoirs and 5 islands in the county.[5]

Towns

Fairfax County has 3 incorporated towns. With their estimated 2025 populations, they are: Herndon (25,506, part), Vienna (16,691), Clifton (241).[6] In Virginia, towns remain part of the county around them, unlike independent cities. "Part" means only the share of the town inside this county.

Frequently asked questions

What is the county seat of Fairfax County?
Fairfax.

What is the population of Fairfax County?
About 1,167,873 people in 2025, according to the U.S. Census Bureau.

How big is Fairfax County?
About 391 square miles of land, plus 15.4 square miles of water.

References

Official website: www.fairfaxcounty.gov

Boundary on the map: Census TIGERweb. See all counties and cities on the map.