A backlight unit that allows a slimmer design for a display device is presented. The backlight unit includes: a bottom chassis; a bracket accommodated in the bottom chassis and positioned at an edge of the bottom chassis; a light source unit including a substrate fixedly positioned on the bracket and a light source mounted on the substrate, the light source protruding toward a bottom of the bottom chassis; and a light guide plate disposed in the bottom chassis and transmitting light from the light source.