FC Seoul (Korean: FC 서울) is a South Korean professional football club based in Seoul that competes in the K League 1, the top flight of South Korean football. The club is owned by GS Sports, a subsidiary of GS Group. Since 2004, FC Seoul have played its home games at the Seoul World Cup Stadium in Seoul's Mapo District.

The club was founded as Lucky-Goldstar Football Club in 1983, by the Lucky-Goldstar Group, and was later renamed as LG Cheetahs in 1990. Due to the K League decentralization policy in 1996, the club was relocated to the Seoul's satellite city of Anyang for eight years, before returning to Seoul in 2004. FC Seoul have won six K League titles, two FA Cups, two League Cups and one Super Cup. Internationally, the club reached the AFC Champions League final on two occasions, in 2001–02 and 2013.

FC Seoul is one of the most successful and popular clubs in the K League 1, with financial backing from the GS Group. In 2012, the club was evaluated as the most valuable football brand in the K League. Their main rivals are Suwon Samsung Bluewings, with whom they contest the Super Match.