Hydrotherapy, formerly called hydropathy and also called water cure, is a branch of alternative medicine (particularly naturopathy), occupational therapy, and physiotherapy, that involves the use of water for pain relief and treatment. The term encompasses a broad range of approaches and therapeutic methods that take advantage of the physical properties of water, such as temperature and pressure, to stimulate blood circulation, and treat the symptoms of certain diseases.

Various therapies used in the present-day hydrotherapy employ water jets, underwater massage and mineral baths (e.g. balneotherapy, Iodine-Grine therapy, Kneipp treatments, Scotch hose, Swiss shower, thalassotherapy) or whirlpool bath, hot Roman bath, hot tub, Jacuzzi, and cold plunge.