Oxygen therapy includes a wide range of therapies that utilise oxygen in various forms to promote healing and destroy pathogens in the body. Therapies are grouped according to the type of chemical processes involved and an equally wide array of techniques for administration exists. Oxygen therapy is based on the fact that all human cells, tissues, and organs need oxygen to function, and it is believed that a lack of oxygen on the cellular level can contribute to cancer and other maladies.

Most oxygen therapies, such as hyperbaric oxygen therapy, in which the patient is placed in a chamber with highly concentrated oxygen, or ozone therapy, in which a mixture containing ozone is injected into the patient, must be administered under clinical supervision. The possible indications that may be treated by such therapies are growing, although most uses of this therapy remain unproven.