Coordinates: 38°53′57″N 77°01′44″W / 38.89908°N 77.02897°W / 38.89908; -77.02897

The Washington Metro, commonly called Metro and branded Metrorail, is the rapid transit system serving the Washington, D.C. metropolitan area in the United States. It is administered by the Washington Metropolitan Area Transit Authority (WMATA), which also operates Metrobus service under the Metro name. Besides the District, Metro serves several jurisdictions in Maryland and Virginia. In Maryland, Metro provides service to Montgomery and Prince George's counties; in Virginia, to Fairfax and Arlington counties and the independent city of Alexandria. The system is currently being expanded into Loudoun County, Virginia. The Metro service area is largely coextensive with the inner ring of the Washington metropolitan area. Opened in 1976, the network now includes six lines, 91 stations, and 117 miles (188 km) of route.

Metro is the second-busiest rapid transit system in the United States in number of passenger trips, after the New York City Subway. There were 215.3 million trips, or 712,843 trips per weekday, on Metro in fiscal year 2015. In June 2008, Metro set a monthly ridership record with 19,729,641 trips, or 798,456 per weekday. Fares vary based on the distance traveled, the time of day, and the type of card used by the passenger. Riders enter and exit the system using a stored-value card in the form of a paper magnetic stripe farecard or a proximity card called SmarTrip.