The present invention relates to a coaxial waveguide electrodeless lamp. The lamp is formed in analogy to coaxial waveguide cables, with an outer conductor, a central conductor, and a gas-fill vessel made of dielectric material between the outer conductor and the inner conductor. The gas-fill vessel is substantially hollow and filled with substances that form a plasma and emit light when RF radiation carried by the central conductor and ground conductor interacts with the substances in the gas-fill vessel. The present invention also relates to a leaky waveguide electrodeless lamp. The lamp is formed in analogy to leaky waveguides, with a conductor, a ground conductor, and a gas-fill vessel made of dielectric material butted against the conductor and encompassed by the ground conductor. The leaky waveguide electrodeless lamp emits light from a plasma similar to light-emission action of the coaxial waveguide electrodeless lamp described above.