A wavelength conversion element includes a wavelength conversion layer containing a plurality of phosphor particles and an inorganic binder that bonds the phosphor particles to each other and a substrate that holds the wavelength conversion layer and contains alumina and air cavities. The substrate has an apparent air cavity ratio that is greater than or equal to 10% and smaller than or equal to 30%. The substrate has a median diameter of particles of the alumina that is greater than or equal to 0.1 μm and smaller than or equal to 1.0 μm.