An organic light emitting device including a first electrode, a hole transport region on the first electrode, a light emission layer on the hole transport region, a buffer layer on the light emission layer, an electron transport region on the buffer layer, and a second electrode on the electron transport region. The buffer layer includes at least one selected from the group consisting of a carbazole derivative, a phenanthroline derivative, a triazole derivative, and a quinolinolato-based metal complex.