K4 League
The K4 League is the fourth-highest division in the South Korean football league system. It is regarded as the successor to the K3 League Basic, the second division of amateur K3 League founded in 2017.
Since 2021, Korea Football Association has allowed reserve teams of the K League to join the K4 League.
Competition format
All participating clubs play home and away season in the K4 League. The promotion and relegation system exists between the K3 League and the K4 League, but does not exist between the K4 League and the amateur K5 League, although there are plans to impement it by 2027.For the 2025 season, the winner of the league will be crowned champions without a playoff and gain automatic promotion. The 2nd-placed team may gain promotion via a two-game playoff series against the 14th-place team in the 2025 K3 League.
Also for the 2025 season, and following the example of K League, match day squad lists have increased from 18 to 20 players. At least three players must be Korean nationals, aged 23 or younger, and at least one of the three must be in the starting eleven. The Asian player quota has been removed, and teams may now include 4 foreign players of any nationality.
K4 League teams are allowed to recruit professional players who choose to do social service instead of military service.
Clubs
Current clubs
Suspended clubs
Former clubs
The following clubs are not in the K4 League as of the 2026 season.| Club | Last season | Reason |
| Paju Citizen | 2020 | Promoted to K3 League |
| Ulsan Citizen | 2020 | Promoted to K3 League |
| Pocheon Citizen | 2021 | Promoted to K3 League |
| Siheung Citizen | 2021 | Promoted to K3 League |
| Yangpyeong FC | 2022 | Promoted to K3 League |
| Chuncheon Citizen | 2022 | Promoted to K3 League |
| Yeoju FC | 2023 | Promoted to K3 League |
| Jeonbuk Hyundai Motors B | 2024 | Promoted to K3 League |
| Dangjin Citizen | 2025 | Promoted to K3 League |
| Icheon Citizen | 2020 | Dissolved |
| Goyang Citizen | 2021 | Dissolved |
| FC Namdong | 2022 | Dissolved |
| Goyang KH | 2022 | Dissolved |
| Busan IPark Futures | 2023 | Dissolved |
| Gangwon FC B | 2023 | Dissolved |
| Goyang Happiness | 2023 | Dissolved |
| Daejeon Hana Citizen B | 2024 | Dissolved |
| Jeonju Citizen | 2024 | Dissolved |
| FC Sejong | 2024 | Dissolved |
| Seoul Nowon United | 2024 | Dissolved |
| Yeoncheon FC | 2025 | Dissolved |
| Daegu FC B | 2025 | Dissolved |