An OLED including a substrate; a circuit region; reflective metal layers on the circuit region and including first to third reflective metal layers spaced apart from each other; an insulating layer including first to third insulating regions covering upper surfaces of the reflective metal layers and having a first to third thicknesses that are different from one another; first to third via plugs penetrating through the insulating layer to contact the reflective metal layers, first electrodes in contact with the via plugs, and covering a portion of an upper surface of the insulating layer; an organic light emitting layer on the first electrodes; and a second electrode on the organic light emitting layer, wherein the first to third via plugs include tungsten.