An optical filter includes a colloidal crystal layer including: a plurality of particles including at least one of an inorganic material or a resin material; and a binder disposed between the plurality of particles. The optical filter reflects a part of light in the wavelength range of 300 nm or more and less than 800 nm. A multiplex optical filter includes multiple optical filters. A light emitting device includes the optical filter and a light source, and a part of primary light emitted from the light source is transmitted through the optical filter.