Chantilly is a census-designated place (CDP) in western Fairfax County, Virginia, United States.

It is located between Centreville to the south, Herndon and Reston to the north and northeast, respectively, and Fairfax 7 miles (11 km) to the southeast.

U.S. Route 50 and Virginia State Route 28 intersect in Chantilly, and these highways provide access to the Dulles/Reston/Tysons Corner technology corridor and other major employment centers in Northern Virginia and Washington, D.C. Chantilly was home to a number of colonial plantations in the 1700s, including the Sully Plantation (now the Sully Historic Site) built by Richard Bland Lee I.

Stuart and her husband Charles Calvert Stuart, whom she had married in 1816, constructed the Chantilly Plantation and named it after the Westmoreland County plantation owned by her grandfather, Richard Henry Lee, a signer of the Declaration of Independence.

During the Civil War, federal troops destroyed by fire the Chantilly Plantation manor house.

One building remains, a stone house across Route 50 from the Greenbriar Shopping Center.

After the war, Cornelia Stuart, who had become deeply in debt, sold her 1,064-acre (431 ha) Chantilly estate.

During the American Civil War on September 1, 1862, the Battle of Chantilly (or Ox Hill) was fought nearby.

"Stonewall" Jackson to cross Bull Run on August 31 and sweep around the position of Major General John Pope's Union Army of Virginia at Centreville.

During September 1, Pope, apprised of Jackson's movement, began to withdraw toward Fairfax Court House.

During the ensuing battle, which was fought amid a raging storm, both Union generals Stevens and Kearny were killed.

The fighting ended at dusk, and Pope's army continued its withdrawal to Fairfax and subsequently to the Washington defenses.

[11] At the 2020 census (some information from the 2022 American Community Survey) there were 24,301 people, 7,716 housing units and 7,187 households residing in the CDP.

[14] The American Registry for Internet Numbers is headquartered adjacent to Washington Dulles International Airport, near Chantilly.