An organic light-emitting device is provided to include: a first electrode; a second electrode facing the first electrode; an organic layer between the first electrode and the second electrode, the organic layer including an emission layer; and at least one organometallic compound represented by Formula 1:

M1M2L,  Formula 1

wherein, in Formula 1, M1 is a first metal center, M2 is a second metal center, and L is a ligand including a first ligand site coordinated to the first metal center and a second ligand site coordinated to the second metal center, and the first ligand site and the second ligand site are linked by an indoloindole derivative.