A wavelength conversion plate includes a conversion region and a reflection region on a base surface. The conversion region includes a wavelength conversion member configured to receive excitation light and generate a color different from a color of the excitation light. The reflection region is configured to reflect the excitation light. The reflection region includes a transmissive diffusion surface, a transmissive layer, and a reflection surface. The transmissive diffusion surface is configured to diffuse the excitation light. The transmissive layer is configured to transmit the excitation light. The reflection surface is configured to reflect the excitation light. The transmissive diffusion surface is in a position separate from a surface closer to the base surface, of the wavelength conversion member, toward a direction from which the excitation light is incident.