A castle once located in Myoukou City, Niigata Prefecture belonging to vassals of the Uesugi Clan.

The date of its construction is undetermined, but during the 1500s the Uesugi (Nagao) Clan used it as a defensive fortress to protect and service the highway through the northern provinces.

During the Otate no Ran, Horie Munechika welcomed Uesugi Kagetora into the castle, seated on the only viable escape route into the Kantou, after the surrender of Kasugayama Castle to Uesugi Kagekatsu. However, Munechika had already been persuaded to betray Kagetora, and he set fire to the outer citadel before evacuating. Samegao fell to Kagekatsu's general offensive two days later.