Minakuchi Castle (Minakuchi-jō), also known as Hekisui Castle, is a hirashiro (castle on a plain) located in Kōka, Shiga Prefecture, Japan. Minakuchi Castle was constructed in 1634 by Tokugawa Iemitsu as a way station he could stay at during his travels between Kyoto and Edo (modern day Tokyo) on the Tōkaidō Road as the fiftieth stop. It was built in a similar fashion to Nijō Castle. Katō Akitomo became lord of Minakuchi Castle in 1682 and his descendants ruled it until the Meiji Restoration, when parts of it were sold and dismantled. As the castle was built for the Shōgun, the Katō never used the palace in the honmaru (innermost bailey), instead constructing one in the ninomaru (second bailey).