Rudkhan Castle (Persian: قلعه رودخان; Gilaki: رودخان دژ), also Roodkhan Castle, is a brick and stone medieval fortress in Iran that was built to defend against the Arab invaders during the Muslim conquest of Persia.

With the fall of the Sasanian Empire, this area became a defensive position against the Arabs in the then-newly established Tabarestan.

Located 25 km southwest of Fuman city north of Iran in Gilan province, it is a military complex which was constructed during the Sasanian era (224-651), and later rebuilt in 1096 by the Nizari Isma'ilis for use by the Assassins.

The eastern part of the castle includes twelve entrances, a prison, an emergency door, a bath and a catchment.

The western part has twelve entrances, the spring, the pond, the reservoir, the cold storage, the bath, the royal water basin and several residential units surrounded by towers and fortifications.