Ronald Reagan Washington National Airport (IATA: DCA, ICAO: KDCA, FAA LID: DCA), also known as National Airport, Washington National, Reagan National Airport, DCA, Reagan, or simply National, is a national airport in Arlington, Virginia, across the Potomac River from Washington, D.C. It is the smaller of two airports operated by the Metropolitan Washington Airports Authority that serve the National Capital Region (NCR) around Washington (the larger airport being Washington Dulles International Airport about 25 miles (40 km) to the west in Virginia's Fairfax and Loudoun counties). The airport is 5 miles (8.0 km) from downtown Washington D.C. and the border is visible from the airport.

The airport's original name was Washington National Airport. Congress adopted the present name to honor President Ronald Reagan in 1998. MWAA operates the airport with close oversight by the federal government due to its proximity to the national capital.

Flights into and out of the airport are generally not allowed to exceed 1,250 statute miles (2,010 km) in any direction nonstop, in an effort to send coast-to-coast and overseas traffic to Washington Dulles International Airport, though there are 40 slot exemptions to this rule. Planes are required to take unusually complicated paths to avoid restricted and prohibited airspace above sensitive landmarks, government buildings, and military installations in and around Washington, D.C., and to comply with some of the tightest noise restrictions in the country.

The airport's small size constrains its capacity, but Reagan National currently serves 91 nonstop destinations. Reagan is a hub for American Airlines. The airport has no United States immigration and customs facilities; the only scheduled international flights at the airport are those from airports with U.S. Customs and Border Protection preclearance facilities, which generally encompasses flights from major airports in Canada and from some destinations in the Caribbean. Other international passenger flights to the Washington, D.C., area use Washington Dulles International Airport or Baltimore–Washington International Thurgood Marshall Airport. Prior to the COVID-19 pandemic, there were five scheduled international routes to cities in Canada, the Bahamas, and Bermuda; these are planned to resume in 2021.

The airport served 23.5 million passengers in 2018. In 2019, DCA served 23,945,527 passengers, an increase of 1.8% over 2018, and a new passenger record for the airport.