Provided are an organometallic compound, an organic light-emitting device including the organometallic compound, and an apparatus including the organic light-emitting device. The organometallic compound may be represented by the formula M11 M12 (L11)n11(L12)n12, wherein M11 and M12 are each independently selected from a Period 1 transition metal, a Period 2 transition metal, and a Period 3 transition metal; L11 is a ligand represented by Formula 1-1 shown below, L12 is selected from a monodentate ligand and a bidentate ligand, n11 is 1, and n12 is selected from 0, 1, 2, 3, and 4.