An organic light-emitting device includes a first electrode, a second electrode facing the first electrode, and an emission layer disposed between the first electrode and the second electrode. An electron transport region is between the second electrode and the emission layer. The electron transport region includes an electron injection layer including a first component including at least one halide of an alkali metal (Group I), a second component including at least one organometallic compound, and a third component including at least one of a lanthanide metal or an alkaline earth metal (Group II).