Abstract: An apparatus for producing ozone from oxygen includes at least one discharge electrode and counterelectrode which are separated by a dielectric of high heat conductivity and tightly bear on the dielectric that is cooled in a direct manner. The discharge electrode, around which oxygen flows, forms a non-closed surface and is in the form of a wire. By applying an electric field, the discharge electrode triggers a discharge in the gas space surrounding the discharge electrode and on the dielectric. The discharge electrode is made of molybdenum, tungsten, niobium or tantalum and is directly exposed to the oxygen flow.