An illumination system includes: a light source that emits light; and a light guide that introduces the light through a light-incident end face facing the light source and that lets out the light from a light-exiting surface adjacent to the light-incident end face. The light source is disposed adjacent to the light-incident end face and in the position shifted from the center of the width of the light guide intersecting the direction in which the light source emits light. The light-incident end face of the light guide has at least one projection or recess in the direction intersecting the light-exiting direction of the light source. The projection or recess has an asymmetrical shape inclined in the direction intersecting the light-exiting direction of the light source. The projection or recess is inclined in one of directions intersecting the light-exiting direction of the light source.