A flat discharge lamp transmitting radiation in ultraviolet or visible, including first and second flat, or substantially flat, glass elements substantially parallel to each other and defining an internal space filled with gas, the first and/or second glass element being made of a material that transmits the radiation; at least one first electrode and at least one second electrode, which may be at different potentials and may be supplied by an AC voltage, the first and second electrodes being associated with one or more main faces of the first glass element, the first and second electrodes being essentially elongate and substantially parallel to one another, and separated by at least one interelectrode space of given width substantially constant; and at least one third electrode which may be at a given potential associated with a main face of the second glass element and at least partly occupying, in projection, the interelectrode space.