An organic light emitting diode display includes: a substrate; an interlayer insulating layer on the substrate; driving source and drain electrodes on the interlayer insulating layer and facing each other; a planarizing layer on the interlayer insulating layer; a pixel electrode on the planarizing layer and including a reflective electrode; a pixel defining layer on an edge portion of the pixel electrode and the planarizing layer, and including an opening for exposing the pixel electrode and a reflective hole for exposing a part of the interlayer insulating layer; an organic emission layer on the pixel electrode within the opening; a common electrode on the organic emission layer and the pixel defining layer and within the reflective hole, and including a transparent electrode; and an optical sensor under the substrate, in which the reflective hole moves light emitted from the organic emission layer to the optical sensor under the substrate.