K League 1

K League 1 is contested by 12 clubs under the current format — fewer than most other top divisions among the major Asian leagues, and similar in scale to the Scottish Premiership. Each club plays the others three times across the regular season, for 33 matches in total. The league then splits into a Championship Round (top six) and a Relegation Round (bottom six), with each club playing five further matches against the other clubs in its half of the table. The full season is 38 matches per club.

The league began in 1983 as the Korean Super League, Asia's first professional football league. It was renamed several times before adopting the K League branding in 1998. The professional system was split into two divisions in 2013, when the top tier became K League Classic, and the division was rebranded as K League 1 in 2018. The competition is organised by the Korea Professional Football League, with the wider national football structure governed by the Korea Football Association.

After all 12 clubs have played each other three times — once at home and twice away, or twice at home and once away, depending on the fixture balance — the table is divided into two halves. The top six clubs form the Championship Round and play five more matches each against the other five clubs in the top half. The bottom six clubs form the Relegation Round and do the same against the other bottom-half clubs. The total of 33 + 5 = 38 matches per club gives the current K League 1 season the same length as many larger leagues.

The format is comparable to the Scottish Premiership's split, although the two systems developed separately. K League 1's split format is useful in a compact 12-club league because it keeps the title race, continental qualification places, and relegation battle concentrated in the final rounds. The format should be treated as the current 12-club structure rather than a permanent rule, because K League 1 is scheduled to expand to 14 clubs from 2027.

In a normal 12-club season, K League 1 usually combines automatic relegation with promotion and relegation play-offs. The 2026 season is unusual because Gimcheon Sangmu are set to be relegated to K League 2 at the end of the season as part of the league's restructuring. If Gimcheon finish bottom, no additional K League 1 club is automatically relegated. If Gimcheon finish above bottom, the 12th-placed club enters a promotion and relegation play-off against a K League 2 play-off side.

K League 2 is contested by 17 clubs in 2026. The top two clubs are automatically promoted to K League 1, while the clubs finishing third to sixth enter the K League 2 play-off route. Below the two professional divisions are the K3 League and K4 League, which form the semi-professional layers of the Korean football pyramid. The lower tiers were reorganised in 2020 as part of wider Korean football reforms, giving the country a more complete league structure beneath the professional game.

K League 1 places in Asian competition are allocated through league position and the Korea Cup, subject to AFC club competition rules and licensing requirements. For the 2026-27 AFC club season, K League clubs received five Asian places: three direct entries to the AFC Champions League Elite league stage, one AFC Champions League Elite play-off place, and one direct place in AFC Champions League Two. Because AFC slot allocations can change, this is best understood as the current allocation rather than a fixed rule for every season.

Korean clubs have been among the most successful in Asian club football. South Korean clubs have won the continent's top club competition 12 times, including Daewoo Royals in 1985-86, Seongnam Ilhwa Chunma in 1995 and 2010, Pohang Steelers in 1997, 1998 and 2009, Suwon Samsung Bluewings in 2001 and 2002, Jeonbuk Hyundai Motors in 2006 and 2016, and Ulsan HD in 2012 and 2020. FC Seoul have reached the final but have not won the competition.

The Korean Super League was launched in 1983 with five founding teams, using a touring format in which matches were played in different cities. It was Asia's first professional football league, predating Japan's J.League and the modern Chinese Super League. Hallelujah FC won the inaugural 1983 title. The league moved to a home-and-away system in 1987 under the name Korean Professional Football League, then went through several name changes before adopting the K League brand in 1998.

The K League was split into two divisions in 2013, with the top tier becoming K League Classic. The K League 1 name was adopted in 2018. The competition has also faced difficult moments, most notably the wide-ranging 2011 K League match-fixing scandal, which led to major disciplinary action and reforms. Despite those problems, Korean clubs have remained major forces in Asian continental football, with 12 titles in the continent's top club competition.