An organic light-emitting device including: a first electrode; a second electrode facing the first electrode; and an organic layer between the first electrode and the second electrode and including an emission layer, wherein the organic layer includes: i) a hole transport region between the first electrode and the emission layer, and including at least one selected from a hole injection layer, a hole transport layer, an emission auxiliary layer, and an electron blocking layer, and ii) an electron transport region between the emission layer and the second electrode and including an electron transport layer, in addition to at least one selected from a hole blocking layer, an electron control layer, a buffer layer, and an electron injection layer, wherein the electron transport region includes a compound represented by Formula 1: