An organic light-emitting device includes: a first electrode; a second electrode facing the first electrode; an emission layer between the first electrode and the second electrode; 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 hole transport region includes a first compound, the emission layer includes a second compound and a third compound, and the electron transport region includes a fourth compound and a fifth compound. An organic light-emitting device according to the one or more embodiments may have high efficiency and long lifespan.