Chantilly is an unincorporated community located in western Fairfax County and southeastern Loudoun County of Northern Virginia. Chantilly is part of the Washington metropolitan area and is approximately 24 miles from Washington, D.C.

According to the United States Census Bureau, the CDP has a total area of 11.7 square miles, all of it land. Chantilly has some land area that is located in Loudoun County, Virginia. Chantilly is served by US-50, the Fairfax County Parkway, and Virginia State Route 28 (Sully Road).

Chantilly is home to Washington Dulles International Airport, which serves Washington, D.C. It is also the location of the Steven F. Udvar-Hazy Center annex of the National Air & Space Museum and the headquarters of the National Reconnaissance Office. Chantilly was also home to the annual Bilderberg summit in 2008 and 2012.

Residents of the CDP go to Fairfax County Public Schools. Rocky Run Middle School, Franklin Middle School, and Chantilly High School are located within the CDP. Westfield High School is a large high school located outside of the CDP. Fairfax County Public Library operates the Chantilly Regional Library in the CDP.