An organic light-emitting device includes a first electrode, a second electrode facing the first electrode, and an organic layer disposed between the first electrode and the second electrode, the organic layer including an emission layer, 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 electron transport region includes a first layer that includes a metal oxide and a metal halide, and wherein the first layer is not in direct contact with the emission layer.