The growth of highly crystalline LaB₆ films with an excellent optical response and low loss is reported, which will be useful for high‐performance photothermal device applications when combined with their inherent refractory properties. Optimum growth parameters for realizing uniaxial and coherent LaB₆ thin films, exhibiting an excellent plasmonic response for near‐ to mid‐infrared device applications, are established. Numerical electromagnetic simulations of the epitaxial LaB₆ nanostructures revealed that the electromagnetic field at the LaB₆ surface can be as high as that of the Au nanostructures. Furthermore, the LaB₆ nanostructures show resonance in the visible (red) to mid‐infrared region comparable to those of Au with the added advantage of improved temperature stability that can withstand harsh photothermal device operations.