An organic light emitting device including an anode; a hole transport region on the anode; an emission layer on the hole transport region; an electron transport region on the emission layer; and a cathode on the electron transport region, wherein the hole transport region includes: a first hole transport layer including a first hole transport material represented by the following Formula 1 or a second hole transport material represented by the following Formula 2; and a second hole transport layer on the first hole transport layer, the second hole transport layer including a third hole transport material represented by the following Formula 3 or a fourth hole transport material represented by the following Formula 4: