Oslo Airport, Gardermoen (IATA: OSL, ICAO: ENGM) (Norwegian: Oslo lufthavn, Gardermoen) is the principal airport serving Oslo, Norway. Oslo is also served by the low-cost Sandefjord Airport, Torp and Moss Airport, Rygge. Gardermoen acts as the main domestic hub and international airport for Norway, and is the second-busiest airport in the Nordic countries. Being a hub for Scandinavian Airlines and Norwegian Air Shuttle, and a focus city for Widerøe, it connects to 28 domestic and more than 100 international destinations. More than 21 million passengers traveled through the airport in 2011, making Gardermoen the nineteenth-busiest airport in Europe.
The airport is located at Gardermoen in Ullensaker, 19 nautical miles (35 km; 22 mi) northeast of Oslo. It has two parallel roughly north–south runways measuring 3,600 metres (11,800 ft) and 2,950 metres (9,680 ft) and 71 aircraft stands, of which 34 have jet bridges. The airport is connected to the city center by the high-speed Gardermoen Line served by mainline trains and Flytoget. The civilian facilities are owned by Oslo Lufthavn AS, a subsidiary of the state-owned Avinor. Also at the premises is Gardermoen Air Station, operated by the Royal Norwegian Air Force.
Oslo Airport, Gardermoen is the largest and busiest of three major international airports located around Oslo. The others are Sandefjord Airport, Torp in the southwest and Moss Airport, Rygge in the southeast.
The area where Oslo Airport, Gardermoen is located was taken into use by the Norwegian Army in 1740, with the first military airport facilities being built during the 1940s. Gardermoen remained a secondary reserve and charter airport to Oslo Airport, Fornebu until 8 October 1998, when the latter closed and an all-new Gardermoen opened, costing NOK 11.4 billion. An expansion with a new terminal building and a third pier is scheduled to open in 2017.

