Hayashi castle was a 15th-century castle, (alternatively known as Hayashi-jo, Fukuyama-jo) in Satoyamabe village, Matsumoto city, Nagano, Japan. A mountain-type castle, it is now largely in ruins. The site is sometimes regarded as one castle, or two castles, Hayashikojo (the small castle) and Hayashiohjo (the larger castle).
The castle Hayashi (Hayashi-jo, Fukuyama-jo, or Hayashikojo and Hayashiohjo) is considered to be in the Satoyamabe village but also in Matsumoto city, located in the Nagano region of the island nation.