An illuminator includes: a light source that emits light; a first lens array including a plurality of first lenslets; a second lens array including a plurality of second lenslets corresponding to the plurality of first lenslets; a polarization conversion element that converts light fluxes from the second lens array into polarized light fluxes and outputs the polarized light fluxes; and a superimposing lens that superimposes sub-light fluxes from the polarization conversion element, wherein the plurality of first lenslets and the plurality of second lenslets are each arranged in a matrix, the polarization conversion element is formed of a plurality of columns of polarization conversion units that convert the light fluxes from the plurality of second lenslets into the polarized light fluxes on a column basis, and the number of columns of the polarization conversion units is fewer than the number of columns of the first lenslets and the second lenslets.