We present a novel method to estimate the light source direction and relight a face texture image of a single 3-D model under arbitrary unknown illumination conditions. We create a virtual irradiance sphere to detect the light source direction from a given illuminated texture image using both normal vector mapping and weighted bilinear interpolation. We then induce a relighting equation with estimated ambient and diffuse intensity. We provide the result of a series of experiments on light source estimation, relighting, and face recognition to show the efficiency and accuracy of the proposed method in restoring the shading and shadow areas of a face texture image. Our approach for face relighting can be used for illuminant-invariant face recognition applications.