The Mysterious Murasame Castle

is a video game developed and published by Nintendo for the Famicom Disk System on April 14, 1986.

Nazo no Murasame-jō was one of the earliest games for the FDS, and was one of the first original titles along with The Legend of Zelda. However, unlike the latter, Nazo no Murasame-jō never saw release outside of Japan.