The Camden Line is a MARC commuter rail line that runs for 39 mi (63 km) between Union Station, Washington, D.C., and Camden Station, Baltimore, Maryland, over the CSX Capital Subdivision and Baltimore Terminal Subdivision. The Baltimore & Ohio Railroad began running commuter service from Baltimore to Ellicott City over part of the current line's trackage on May 24, 1830, making this corridor one of the country's oldest rail routes still in operation. The line was extended to Washington on August 25, 1835. The Camden Line is the shortest MARC line. As of 2019, the Camden Line is a weekday-only service.

Greenbelt station is a Washington Metro and MARC station in Prince George's County, Maryland. The station is the northeastern terminus of the Green Line of the Washington Metro. MARC commuter rail trains on the Camden Line also stop at Greenbelt on a set of tracks parallel to the Metro tracks.