A sanatorium (from Latin sānāre 'to heal, make healthy'), also sanitarium or sanitorium, are antiquated names for specialised hospitals, for the treatment of specific diseases, related ailments and convalescence. Sanatoriums are often in a healthy climate, usually in the countryside. The idea of healing was an important reason for the historical wave of establishments of sanatoriums, especially at the end of the 19th- and early 20th centuries. One sought, for instance, the healing of consumptives, especially tuberculosis (before the discovery of antibiotics) or alcoholism, but also of more obscure addictions and longings of hysteria, masturbation, fatigue and emotional exhaustion. Facility operators were often charitable associations such as the Order of St. John and the newly founded social welfare insurance companies.

Sanatoriums should not be confused with the Russian sanatoriums from the time of the Soviet Union, which were a type of sanatorium resort residence for workers.