It are a group of nine parallel association football leagues in Japan that are organized on the regional basis. They form the fifth and sixth tier of the Japanese association football league system.
Teams with "Un" are feeder (or "B") teams for their universities' main football teams.
In the Regional Leagues, first divisions equal to Japanese fifth tier of league football, while second divisions equal to the sixth tier. So, regional leagues who only have one single division, such as Shikoku, have teams going straight from the prefectural top divisions to the fifth tier in case of a promotion.
^2025シーズンJ3クラブライセンス判定結果について(J3入会を希望するクラブ) [Regarding the results of the 2025 J3 Club License Assessment (Clubs wishing to join J3)]. J.League (in Japanese). J.League. September 24, 2024. Retrieved September 25, 2024.