An organic light-emitting device, including: an anode and a cathode opposite each other, a first stack and a second stack between the anode and the cathode, and a charge generation layer between the first stack and the second stack, the charge generation layer including an n-type charge generation layer and a p-type charge generation layer, wherein the p-type charge generation layer includes one first organic material, wherein the n-type charge generation layer includes a second organic material and an n-type dopant, wherein the n-type charge generation layer is divided into a first region contacting the first stack, a second region contacting the p-type charge generation layer, and a third region between the first region and the second region, and wherein a dopant content of the n-type dopant is stepwise increased in an order of: the first region, the third region, and the second region.