Lorton is a census-designated place (CDP) in Fairfax County, Virginia, United States. The population was 17,786 at the 2000 census.

Geography
As of the census of 2000, there were 17,786 people, 5,663 households, and 3,884 families residing in the CDP. The population density was 554.7/km² (1,436.6/mi²). There were 5,892 housing units at an average density of 183.8/km² (475.9/mi²). The racial makeup of the CDP was 48.95% White, 34.66% African American, 0.29% Native American, 7.63% Asian, 0.13% Pacific Islander, 3.92% from other races, and 4.42% from two or more races. Hispanic or Latino of any race were 9.74% of the population.
There were 5,663 households out of which 42.5% had children under the age of 18 living with them, 49.5% were married couples living together, 15.2% had a female householder with no husband present, and 31.4% were non-families. 23.3% of all households were made up of individuals and 1.4% had someone living alone who was 65 years of age or older. The average household size was 2.68 and the average family size was 3.21.
In the CDP the population was spread out with 25.2% under the age of 18, 8.4% from 18 to 24, 45.2% from 25 to 44, 18.6% from 45 to 64, and 2.6% who were 65 years of age or older. The median age was 33 years. For every 100 females there were 125.3 males. For every 100 females age 18 and over, there were 133.6 males.
The median income for a household in the CDP was $60,150, and the median income for a family was $63,821. Males had a median income of $43,586 versus $36,694 for females. The per capita income for the CDP was $25,146. About 5.0% of families and 6.6% of the population were below the poverty line, including 10.5% of those under age 18 and 3.5% of those age 65 or over.