A backlight unit is disclosed. The backlight unit includes a light emitting device, a light guide plate to guide light irradiated from the light emitting device, an optical sheet disposed on a front surface of the light guide plate, a bottom chassis disposed below the light guide plate, a mold frame disposed on a front surface of the optical sheet, and an anti-contact protrusion disposed at the bottom chassis so as to come into contact with the mold frame, thereby allowing the mold frame to be spaced apart from the light guide plate and the front surface of the optical sheet.