The Red Line is a rapid transit line of the Washington Metro system, consisting of 27 stations in Montgomery County, Maryland, and Washington, D.C., in the United States. It is a primary line through downtown Washington and the oldest and busiest line in the system. It forms a long, narrow "U," capped by its terminal stations at Shady Grove and Glenmont.

The Washington Metro, often abbreviated as the Metro and formally the Metrorail, is a rapid transit system serving the Washington metropolitan area of the United States. It is administered by the Washington Metropolitan Area Transit Authority (WMATA), which also operates the Metrobus service under the Metro name. Opened in 1976, the network now includes six lines, 98 stations, and 129 miles (208 km) of route.