A light source apparatus according to an aspect of the present disclosure includes a light source section, a first polarization separator that transmits a first polarization component of first light and reflects a second polarization component of the first light, a second polarization separator that reflects the first polarization component, transmits a third polarization component of second light, and reflects a fourth polarization component of the second light, a diffuser that diffuses the second polarization component and causes the diffused second polarization component, a wavelength converter that converts the wavelength of the first polarization component and causes the second light, and a first phase retarder that is provided in the optical path of the first light between the first polarization separator and the second polarization separator and converts the first polarization component of the first light into the second polarization component.