Ozone therapy is a therapy that has been studied and used for a long time. Ozone is a colourless gas with a pungent odour, an allotropic modification of oxygen (O3) that occurs naturally in the atmosphere (stratosphere and troposphere). In medicine, ozone therapy is used to disinfect and treat diseases, disinfecting the environment to improve oxygen uptake and the immune system. With its strong oxidizing effect, it has been proven to have a beneficial effect for the purpose of disinfection and treatment of various pathological conditions as it improves oxygen uptake. It is used in the treatment of dermatological, infectious and non-degenerative diseases, diseases of the vascular system, in the treatment of some cancers and in orthopaedics. In addition to medical applications, ozone is also used in the food industry and in environmental protection (hygiene, waste and wastewater treatment). Despite its many uses, caution should be exercised with ozone because of its toxicity. The purpose of this work was to present the properties of ozone, its application, the results of therapies in which its effectiveness is possible and to describe the mechanism of its therapeutic action.