An organic light-emitting device including a first electrode; a second electrode facing the first electrode; an emission layer between the first electrode and the second electrode; a hole transport region between the first electrode and the emission layer; and an electron transport region between the emission layer and the second electrode, wherein the hole transport region includes a first compound represented by Formula 1-1 or Formula 1-2, and wherein the electron transport region includes a second compound represented by Formula 2: