Dahlgren is a census-designated place (CDP) in King George County, Virginia, United States. The population was 997 at the 2000 census. The community is located within the Northern Neck George Washington Birthplace American Viticultural Area winemaking appellation established by the United States government.
Since 1918, Dahlgren has been the site of a U.S. Naval base named for Rear Admiral John A. Dahlgren. It was then the "U.S. Naval Proving Ground" but was renamed, after 1950, "U.S. Naval Weapons Laboratory", in 1974, the "Naval Surface Weapons Center","in 1987 the "Naval Surface Warfare Center", and around 1990, as the "U.S. Naval Surface Warfare Center Dahlgren Division (NSWCDD)". In 2006, it was renamed "Naval Support Activity-South Potomac (NSA-SP)", with NSWCDD becoming a tenant command of the base. The "U.S. Naval Space Surveillance Systems" command was located at that base, but was moved in 2006. The AEGIS Training and Readiness Center is currently a tenant command at NSA-SP. The 2-mile long, narrow 2-lane Harry Nice Memorial Bridge funnels interstate traffic across the wide Potomac River at Dahlgren, offering an alternative to using Interstate 95. A sign by the highway announces that a Wal-Mart store is planned for the community.
According to the United States Census Bureau, the CDP has a total area of 1.1 square miles (2.9 km²), all of it land.