Northern Virginia, locally referred to as NOVA or NoVA, comprises several counties and independent cities in the Commonwealth of Virginia in the United States. The region radiates westward and southward from Washington, D.C., the nation's capital, and has a population of 3,257,133 people as of 2023 U.S. Census Bureau estimates, representing over a third of the state's total population. It is the most populous region in both Virginia and the regional Washington metropolitan area.

Communities in the region form the Virginia portion of the Washington metropolitan area and the larger Washington–Baltimore metropolitan area. Northern Virginia has a significantly larger job base than either Washington, D.C. or the Maryland portion of its suburbs, and is the highest-income region of Virginia, with several of the highest-income counties in the nation, including three of the ten highest counties for median household income, according to the 2019 American Community Survey.

Northern Virginia's transportation infrastructure includes two major airports, Ronald Reagan Washington National and Dulles International Airport, several lines of the Washington Metro subway system, the Virginia Railway Express suburban commuter rail system, transit bus services, bicycle sharing and bicycle lanes and trails, and an extensive network of Interstate highways and expressways.

The Pentagon, the headquarters of the U.S. Department of Defense and the world's second-largest office, is located in Arlington County in Northern Virginia. Northern Virginia also houses the George Bush Center for Intelligence, the headquarters for the Central Intelligence Agency in Langley, the United States Patent and Trademark Office in Alexandria, and several large companies, including several major aerospace manufacturing, consulting firms, and defense industry, which serve it and other components of the U.S. federal government.

Tourist attractions in Northern Virginia include various memorials, museums, and Colonial and Civil War–era sites, including Arlington National Cemetery, Fredericksburg and Spotsylvania National Military Park, Manassas National Battlefield Park, Mount Vernon, the National Museum of the Marine Corps, the National Museum of the United States Army, the Udvar-Hazy Center of the National Air and Space Museum, and the United States Marine Corps War Memorial. Other attractions include portions of the Appalachian Trail, Great Falls Park, Old Town Alexandria, Prince William Forest Park, and portions of Shenandoah National Park.

The region is sometimes spelled "northern Virginia", but the U.S. Geological Survey's Correspondence Handbook states that the 'n' in Northern Virginia should be capitalized since it is a place name rather than a direction or general area.

The name "Northern Virginia" does not seem to have been used in the early history of the area. According to Johnston, some early documents and land grants refer to the "Northern Neck of Virginia", a reference to the Northern Neck and describing an area that began at the western shore of the Chesapeake Bay and includes a territory that extended west, including all the land between the Potomac and Rappahannock rivers, with a western boundary called the Fairfax line. The Fairfax line, surveyed in 1746, ran from the first spring of the Potomac River, which remains marked today by the Fairfax Stone, to the first spring of the Rappahannock River, at the head of the Conway River. The Northern Neck was composed of 5,282,000 acres (21,380 km²), and was larger in area than five of the modern U.S. states:

This monument, at the headspring of the Potomac River, marks one of the historic spots of America. Its name is derived from Thomas Lord Fairfax who owned all the land lying between the Potomac and Rappahannock Rivers. The first Fairfax Stone, marked "FX", was set in 1746 by Thomas Lewis, a surveyor employed by Lord Fairfax. This is the base point for the western dividing line between Maryland and West Virginia.