An organic light-emitting device including a first electrode, a second electrode facing the first electrode, and an organic layer disposed between the first electrode and the second electrode, wherein the organic layer includes an emission layer, wherein the organic layer further includes i) an organometallic compound represented by Formula 1, and ii) at least one selected from a first compound represented by Formula 51, a second compound represented by Formula 61, a third compound represented by Formula 81, and a fourth compound represented by Formula 91, wherein Formulae 1, 51, 61, 81, and 91 are the same as described in the specification.