Seongnam FC

In 1975, Sun Myung Moon, the owner of Tongil Group, wanted to found a professional football club in South Korea. After the Korean Super League was founded in 1983, he tried to establish a club to participate in the league but Choi Soon-young, the head of Korea Football Association, ignored Moon's interest due to religious reasons.

Nevertheless, Tongil Group prepared the foundation of a new football club from 1986 and finally obtained a license from Korea Football Association as a club based in Seoul.^[] Tongil Group had initially considered establishing the club in the Honam region but there was objection from the local community.

The club was officially founded on 18 March 1989 as Ilhwa Chunma Football Club, and became the sixth member of the Korean Super League. The foundation ceremony was held in the Sheraton Walkerhill Hotel in Seoul.

The club had signed six players including Ko Jeong-woon and appointed Park Jong-hwan as the head coach. The contract with Park was considered a lucrative deal at the time, with a signing bonus of 100 million KRW paid alongside an annual salary of 48 million KRW.

The club was successful from its beginning, winning its first League Cup three years after its foundation in 1992 and winning three consecutive league titles from 1993 to 1995. In 1995, K League clubs wanted to stop the club's third consecutive title and agreed to change the league format back to two stages with a championship playoffs system; however, Ilhwa Chunma still won the title.

The club won its first Asian title in the same year, defeating Saudi Arabian side Al Nassr in the final to achieve a league and continental double.^[]

The club was forced to move out of Seoul in 1996 following the implementation of the K League decentralization policy. Ilhwa Chunma moved to the city of Cheonan as the city council proposed converting the Cheonan Oryong Stadium into a football-specific stadium and building another sports complex in Baekseok-dong.^[] The club also changed its name to Cheonan Ilhwa Chunma as a part of the policy.

By the end of 1997, Ilhwa was still enjoying success. The club reached the final of the 1996–97 Asian Club Championship and the 1997 Korean FA Cup. However, from 1998, the club went into a slump as a number of core players moved away from the club for various reasons. One of these players was the club's goalkeeper, Valeri Sarychev, who was forced to move as the K League gradually introduced restrictions on appearances by foreign goalkeepers.

As a result, Ilhwa finished at the bottom of the league for two consecutive seasons, in 1998 and 1999. In mid-1999, Cha Kyung-bok offered to resign voluntarily due to the poor results. On 21 November 1999, Cheonan Ilhwa Chunma were crowned as the winners of the 1999 Korean FA Cup after beating Jeonbuk Hyundai Dinos 3-0 in the final, held at Jeju Stadium.

In 2000, the club moved to the Seoul satellite city of Seongnam and renamed themselves to Seongnam Ilhwa Chunma. The move worked out well, as the rejuvenated club went on to win three consecutive K League titles from 2001 to 2003, as well as a league cup title in 2002 and an A3 Champions Cup in 2004. A disappointing 2004 campaign saw them relinquish their title. The club's shock defeat at home to Saudi Arabian side Al Ittihad in the ACL final the same year led to the resignation of their manager Cha Kyung-bok.^[]

Under Kim Hak-bum's management, the club bounced back to the forefront of South Korean football as they claimed their seventh league title in 2006, defeating Suwon Samsung Bluewings 3–1 on aggregate in the championship playoff final. This was their seventh K League title, a record among all the K League clubs.^[]

In the 2007 season, they went undefeated for 22 consecutive league matches — the third longest streak in the history of the K League — before finally being defeated by Suwon Samsung Bluewings 2–1 on 15 July 2007. Seongnam finished the regular season of the 2007 K League Championship in first place but were beaten 4–1 on aggregate in the championship final by Pohang Steelers.

Seongnam's former player Shin Tae-yong returned as caretaker manager in the 2009 season before being officially appointed as manager from the following season as the club's successes continued. Seongnam won the 2010 AFC Champions League, defeating local rivals Suwon in the quarter-finals and going on to beat Iranian side Zob Ahan 3-1 in the final in front of 27,000 fans in Tokyo's National Stadium.

Seongnam added another FA Cup trophy to their collection in 2011, beating Suwon 1–0 in the final.

In October 2013, Lee Jae-myung, the mayor of Seongnam, announced that Seongnam City Council had agreed to take over the club from Ilhwa Sports, and that it would henceforth be known as Seongnam FC. In December 2013, Seongnam City officially took over the club from Ilhwa Co., Ltd.

They changed their symbol from chunma, which was the symbol of the Unification Church, to the magpie, the symbol of the Seongnam city. The yellow color of their uniform was also replaced with black. Their first manager Park Jong-hwan, who had managed the club from 1988 to 1996, returned to the club as manager once again.

The club played the first home game as Seongnam FC on 15 March 2014 against FC Seoul, resulting in a 0–0 draw. Their first post-rebranding victory came on 26 March, when they beat bitter rivals Suwon Samsung Bluewings 2–0. The following month, manager Park Jong-hwan resigned after it was revealed that he had been assaulting players.

After months of confusion, the club appointed Kim Hak-bum, who led the club during their glory years, as manager. His return turned out to be a success, as Seongnam not only escaped relegation but also won their third FA Cup trophy, beating FC Seoul in a penalty shoot-out.

In the 2016 season, after Incheon's win over Suwon FC on the final day of the season, Seongnam finished 11th and were relegated to the second division for the first time in their history after being defeated by Gangwon FC on away goals rule in the promotion-relegation playoffs.

Nam Ki-il was announced as the club's new manager on 6 December 2017, replacing Park Kyung-hoon. He led Seongnam FC to promotion back to the first division just one season after their relegation. Nam resigned his position as the manager of the club on 16 December 2019. Kim Nam-il was appointed as the club's new manager on 23 December 2019 to lead the club in the 2020 K League 1 season.

In 2022, the club was once again relegated to K League 2. The club finished the 2024 K League 2 season at the bottom of the league table, but remained in the league as there is no promotion and relegation between K League 2 and K3 League.