明星院, Buddhist temple in Okegawa, Japan.

Myojo-in is a Shingon Chizan temple in the Kurata area of Okegawa, Saitama Prefecture, whose main hall stands before a huge kaya tree about 31 m tall and an estimated 600 years old, designated a prefectural natural monument. The temple is one of the eleven Kanto Shingon learning centers, and its name comes from the Myojo no Ido well on the grounds.

Founded at the start of the Muromachi period by Ryuson and first called Godaisan Kōgan-ji, the temple held Kurata village as its estate. In 1591 Tokugawa Ieyasu granted it a vermilion-sealed holding of ten koku of rice. In the same year Ina Tadatsugu moved the Muryō-ji Akai-bō from Komuro to Myōjō-in and gave it three chō of surrounding fields, as recorded in a dated Ina Tadatsugu document kept at the Saitama Prefectural Archives.

The temple houses precious cultural artifacts including gold lacquerware dining sets, gold folding screens, and historical documents from the Sengoku and Edo periods, some of which were personally bestowed by Tokugawa Ieyasu himself.

The temple stands in the Kurata district of Okegawa, reachable by the Okegawa city loop bus Benibana GO (east-west outer loop) to the "Higashi 38 Myojo-in-mae" stop. Alternatively, take the Ina town loop bus Inamaru north loop to Shinjuku-Shinden and walk five minutes, or walk fifteen minutes from Uchijuku Station on the New Shuttle. The 31 m kaya tree behind the main hall is a prefectural natural monument.

The temple's name comes from the Myojo no Ido well on its grounds. Villagers told of a heavenly maiden standing in the dawn clouds, a single thread from her hand reaching down to the well; another legend says a morning star flew out of it. The temple also keeps a 31 m kaya tree behind the main hall, said to have been planted as a cutting by founder Ryuson and now a prefectural natural monument.