State Route 645 in Fairfax County, Virginia is a secondary state highway. There are six portions, three of them being major, named Wall Road, Lees Corner Road, Stringfellow Road, Clifton Road, Main Street and Burke Lake Road. There are also numerous overlaps : some include SR 657 / Centreville Road, U.S. Route 50, SR 652, SR 612, and SR 641. A concurrency used to exist at US 29 near Centreville until the 1990s.

Clifton is an incorporated town located in southwestern Fairfax County, Virginia, United States, with a population of 243 at the time of the 2020 census.