2025–26 Thai League 3

The 2025–26 Thai League 3 (known as the BYD Dolphin League III for sponsorship reasons) will be the ninth season of the Thai League 3, the third tier of professional football in Thailand. A total of 68 clubs will participate, divided into six regional groups: Northern (12 clubs), Central (11 clubs), Northeastern (12 clubs), Eastern (12 clubs), Western (11 clubs), and Southern (10 clubs).

The season is scheduled to begin on 13 September 2025 with the opening matches of the Regional Stage. In this stage, clubs compete within their respective regions, with the champions and runners-up from each group advancing to the National Championship Stage. The final phase will feature 12 clubs and conclude with the national final in 2026 (date to be confirmed). The winners, the runners-up, and the winner of the third-place play-off will be promoted to the Thai League 2 for the 2026–27 season.

For sponsorship purposes, the three professional tiers in Thailand have been rebranded for the 2025–26 season as BYD SEALION 6 League I (Thai League 1), BYD SEAL 5 League II (Thai League 2), and BYD DOLPHIN League III (Thai League 3).