An internal combustion engine piston includes a crown surface including a low thermal conductivity part lower in thermal conductivity than a base material. The low thermal conductivity part includes a porous member made of a glass material lower in thermal conductivity than the base material, and impregnated with the base material. A first material is interposed at least partly between the porous member and the base material in the low thermal conductivity part, wherein the first material is water-soluble, and has a higher melting point than the porous member.