Franconia is a census-designated place (CDP) in Fairfax County, Virginia, United States. The population was 18,943 at the 2020 census.Located just southwest of Alexandria, Franconia has existed as a community since the 1870s, when a station by that name opened on the RF&P Railroad; however, like most of the surrounding area, it only began to develop into its present, suburban form in the 1950s. The CDP extends south to just north of the border of Fort Belvoir, encompassing neighborhoods such as Manchester Lakes and Windsor Estates. Street addresses have Alexandria ZIP Codes 22310 and 22315. It is near the Springfield Mall shopping area and the Franconia–Springfield Washington Metro station.