The Loudoun County Commuter Bus, also known as Loudoun County Transit, is a public-transportation service provided by the Loundon County, VA government. The buses operate from Dulles, Leesburg, and Purcellville to Washington Metro stations as well as directly to Rosslyn, VA, The Pentagon, and Washington, D.C.. The service is attractive because the buses, unlike normal traffic, are permitted to travel on the express lanes of the Dulles Toll Road. This allows for a shorter trip and also bypasses commuter tolls. The Loudoun County Commuter Bus accepts payment via SmarTrip, a reloadable transit card issued by the Washington Metropolitan Area Transit Authority.

Loudoun County Transit buses should not be confused with Virginia Regional Transit (VRT) buses, which also serve Loudoun County (among other Virginia counties) and have overlapping bus stops within the county. LC Transit uses long buses (seating around 50) with white and metal trim and display the LC Transit logo (shown above), while VRT buses are short (seating around 15) and have a predominantly white and maroon color scheme, frequently without a logo.