| Season | 2021 |
|---|---|
| Dates | Regular season: 13 March – 13 November 2021 Championship: 17–27 November 2021 |
| Champions | Gimpo FC (1st title) |
| Promoted | Gimpo FC |
| Relegated | Pyeongtaek Citizen |
| Matches played | 214 |
| Goals scored | 479 (2.24 per match) |
| Best Player | Kim Jong-seok[1] |
| Top goalscorer | Kim Jong-seok (15 goals)[1] |
← 2020 2022 → | |
The 2021 K3 League was the second season of the K3 League as a semi-professional league. The 15 participating teams played each other twice, and the bottom team was relegated to the K4 League.