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.