Gassan Shrine (月山神社, Gassan jinja) is a Shinto shrine on Mount Gassan in Yamagata Prefecture, Japan. It was formerly a national shrine of the first rank (国幣大社, kokuhei taisha) in the Modern system of ranked Shinto Shrines. The main kami enshrined here is Tsukuyomi-no-Mikoto. It was established in 593.
The shrine's main festival is held annually on August 14.
Coordinates: 38°32′49″N 140°01′33″E / 38.5469°N 140.0258°E