Mii-dera (三井寺,御井寺), formally called Onjō-ji (園城寺), is a Buddhist temple located at the foot of Mount Hiei, in the city of Ōtsu, in Shiga Prefecture. It is only a short distance from both Kyoto, and Lake Biwa, Japan's largest lake. The head temple of the Tendai Jimon sect, it is something of a sister temple to Enryakuji, at the top of the mountain, and is one of the four largest temples in Japan. Altogether, there are 40 named buildings in the Mii-dera temple complex.
Mii-Dera is temple number 14 in the Kansai Kannon Pilgrimage.