Disclosed herein is a backlight unit including a light guide plate including a light emitting portion to emit light, side surfaces defining corners, and a first light incidence portion and a second light incidence portion to receive light, at least two light emitting modules respectively disposed to face the first light incidence portion and the second light incidence portion, and an optical sheet disposed on the light guide plate, wherein the first light incidence portion is disposed one corner region of the light guide plate, and the second light incidence portion is disposed another corner region of the light guide plate, wherein the first light incidence portion is facing the second light incidence portion or disposed to both sides of one side surface of the light guide plate.