Mii-dera Temple was first established as a Uji-dera Temple (temple built for praying clan's glory) of Ouchi clan in the 7th century, then restored in the 9th century by Enchin, ryugakuso (a priest who studied abroad), who returned from Tang.
三井寺は7世紀に大友氏の氏寺として草創され、9世紀に唐から帰国した留学僧円珍（天台寺門宗宗祖）によって再興された。