The disclosure relates to surface plasmon-polariton waveguides, which can guide ultra-long range surface plasmon-polariton waves. The attenuation of an ultra-long range surface plasmon-polariton waves is much lower than the attenuation of the conventional long range surface plasmon-polariton waves guided with the same kind of metal film or metal strip at the same plasmon-polariton frequency. An exemplary ultra-long range surface plasmon-polariton waveguide disclosed in this disclosure comprises a metal layer, such as a metal film or finite width metal strip, intermediate dielectric layers adjacent to the metal layer, and outer cladding dielectric material. The intermediate dielectric layers redistribute the electromagnetic energy distribution of the surface plasmon-polariton waves so that less of the energy propagates in the metal layer. Therefore, the attenuation of the surface plasmon-polariton wave is reduced. The propagation distance of the ultra-long range surface plasmon-polariton wave can be designed to a desired value by adjusting the thickness and the material property of the intermediate dielectric layers and other parameters related to the waveguide.