Minakuchi Castle, Japanese castle in Koka, Japan

Minakuchi Castle is a Japanese fortress in Koka with a central bailey measuring about 150 meters on each side, ringed by moats and stone walls with watchtowers at the corners. The layout shows the typical design of a feudal lord's residence from the early Edo period.

The castle was built in 1634 by the Tokugawa shogun Iemitsu and served as a way station during his journeys to Kyoto along the strategic Tokaido road. After demolition in the Meiji era, the site was partially rebuilt in 1991.

The Katō clan, rulers of Minakuchi Domain from 1682, kept the shogun's palace in repair in case he returned, but governed from the northwest bailey and never used the honmaru palace, which was dismantled in the Shōtoku era. The castle is also called Hekisui Castle.

The castle is a five-minute walk north from Minakuchi Jonan Station on the Ohmi Railway Main Line. The reconstructed yagura, two gates and stone walls stand near the site of the honmaru, now used as Minakuchi High School's grounds. The surrounding area retains the layout of the old Tōkaidō post station.

The 1991 reconstruction rebuilt the乾 turret on its stone base after the building had been moved to a private house following the castle's abolition; it now holds the Minakuchi Castle Museum. The stone foundations of the turret and the outer bailey gate survive in situ.