A light source apparatus includes a light source section, a first optical layer that transmits first light polarized in a first polarization direction and incident from the light source section and reflects the first light polarized in a second polarization direction and incident from the light source section, a second optical layer that transmits the first light polarized in the first polarization direction and incident from the first optical layer, a third optical layer that transmits the first light polarized in the first polarization direction and incident from the second optical layer, a fourth optical layer that reflects the first light polarized in the first polarization direction and incident from the third optical layer, a diffusion element, and a wavelength converter.