Sasayama Castle (Sasayama-jō) is a Japanese castle in Sasayama, Hyōgo, Japan. Construction of this castle was begun by the order of Tokugawa Ieyasu in 1608 and it was completed in six months. Ikeda Terumasa was in charge of the construction and the plan of the castle was done by Tōdō Takatora. It is said that twenty daimyo were mobilized for the construction.
The castle was so well designed that Ieyasu commanded that the tenshu, or keep, not be constructed because he feared that it would be used as a base against him. The castle was held by the Aoyama clan for 123 years during the Edo period. The first Aoyama lordship of the castle started in 1748, and continued until the castle was torn down in 1871.