To provide a novel prism and lighting system, capable of illuminating a wide range, and capable of attaining illumination of restraining an irregular illuminance from being generated within an illuminated range, even when illuminated over the wide range.

This prism 10 is constituted to form a concave light emitting face of a base part 100 of the prism 10, into a concave shape as the whole, and to bring, in particular, the third light emitting face for connecting the first light emitting face and the second light emitting face in both sides, out of three faces forming the concave shape, into a concave curved face.