Disclosed herein are a backlight unit and a lighting system including the same. The backlight unit includes a first reflector and a bottom cover, a plurality of reflector support parts disposed on the bottom cover, each of the reflector support parts including at least two first and second slanted surfaces adjacent to each other about at least one inflection point, a second reflector disposed on the plural reflector support parts, and a light source module disposed between the first reflector and each of the second reflector.