Gimpo International Airport (IATA: GMP, ICAO: RKSS), formerly rendered in English as Kimpo International Airport, is located in the far western end of Seoul, South Korea, some 15 kilometres (9 mi) west of the central district of Seoul.

Gimpo previously carried the IATA airport code SEL, which is now used by airline reservation systems and travel agencies within the Seoul Metropolitan Area, and was the main international airport for Seoul and South Korea before being replaced by Incheon International Airport in 2001. It now functions as Seoul's secondary airport. In 2015, over 23 million passengers used the airport, making it the third-busiest airport in Korea since being surpassed by Jeju International Airport.

The airport is located south of the Han River in western Seoul. The name Gimpo comes from the nearby city of Gimpo, of which the airport used to be a part.

On 29 November 2003, scheduled services between Gimpo and Haneda Airport in Tokyo resumed with services also operating at Incheon Airport. Services to Shanghai Hongqiao International Airport resumed on 28 October 2007. Services to Kansai International Airport in Osaka, Japan, started on 26 October 2008 with services also operating at Incheon Airport. Services to Beijing Capital International Airport started on 1 July 2011 with services also operating at Incheon Airport. Services to Taipei Songshan Airport started on 30 April 2012.

The airfield was built in 1939 during the Japanese Imperial period as an Imperial Army base. The runways were built on a bed of rocks manually hauled by Korean labourers from Kaihwasan and Yangchan, several miles from the base. Then known as Keijo New Airfield (京城新飛行場), Gimpo was constructed with four runways to supplement the much smaller Keijo Airfield (京城飛行場), which was later known as Yeouido Airport.

Gimpo played a major role during the Korean War, and the USAF designated the airfield as Kimpo Air Base or K-14.

North Korean forces attacked South Korea on 25 June 1950 starting the Korean War. During one of the first Korean People's Air Force (KPAF) attacks on 25 June, a Military Air Transport Service C-54 Skymaster was destroyed on the ground at Gimpo. On 27 June, US naval and air forces began evacuating 748 US diplomats, military dependents, and civilians by air transport from Kimpo and Suwon Airfield. On the afternoon of 27 June, five F-82 Twin Mustangs of the 68th Fighter Squadron and 339th Fighter Squadron were escorting four C-54 Skymaster aircraft out of Kimpo when the C-54s were attacked by five KPAF Lavochkin La-7 fighters. In the subsequent dogfights, three LA-7s were shot down for the loss of no US aircraft in the first air battle of the war. Later that day, four F-80Cs of the 35th Fighter-Bomber Squadron shot down four Ilyushin Il-10s for no losses over Gimpo in the USAF's first jet-aircraft victory.

Gimpo was captured by the KPA shortly after the capture of Seoul on 28 June 1950. On 29 June, eight B-29s of the 19th Bomb Group bombed Gimpo and the Seoul railyards. By July, the KPAF were using the base for attacks on UN forces; on 10 July, seven Yak-7s were hidden at Gimpo and used in strikes against UN positions at Cheongju. The next day, they surprised and damaged several Lockheed F-80s in the area. On 15 July, the US launched an attack on Gimpo, destroying two or three of the seven Yak-7s there and damaging the runway. On 5 August 5th Air Force fighters strafed and bombed Gimpo, destroying 9 aircraft and damaging 9 others.