An organic light-emitting device including: a first electrode; a second electrode facing the first electrode; and an organic layer between the first electrode and the second electrode, the organic layer including an emission layer, wherein the organic layer includes a carbazole-based compound represented by Formula 1A or 1B:




When the carbazole-based compound represented by Formula 1A or 1B is included in the hole transport layer, an organic light-emitting device may have improved driving voltage, efficiency, luminance, and lifespan characteristics.