Ganban'yoku (岩盤浴) is the Japanese term for a popular form of hot stone spa. It is said to have originated in Japan.

Body-sized stones, such as granite, are heated into the floor. Bathers lie clothed on the stones while their bodies gradually heat up.

Like low-temperature saunas, Ganban'yoku are commonly advertised to have a detoxification effect, improve the circulatory system, and are good for the skin. A Ganban'yoku room in a spa would typically be visited after the baths and would be in a clothing-on area with mixed genders.

Many spa facilities, including Spa LaQua at Tokyo Dome City and Urban Quar Spa in Nagoya, have Ganban'yoku rooms.