An optical system of the present disclosure includes: a first optical system that includes a first optical element having a plurality of divided regions having mutually different polarization actions, the first optical element being disposed at a first pupil position in the optical system, and that generates illumination light including a plurality of color light beams in mutually different wavelength bands; a plurality of light valves that each modulates at least one color light beam of the plurality of color light beams included in the illumination light; and a second optical system that includes a second optical element having a plurality of divided regions having mutually different polarization actions, the second optical element being disposed at a second pupil position conjugate to the first pupil position, and on which the plurality of color light beams modulated by the plurality of light valves is incident.