A continuum light emission extending from the infrared to the ultraviolet has been observed in highly excited Xe and Kr crystals. The light is emitted by an electron plasma with an electron density of about 10 to the 18th per cu cm. The kinetic energies of the electrons correspond to an electron temperature of about 2000 K for a lattice temperature of 15 K (Kr) and 60 K (Xe). This electron plasma represents a case of an extreme thermal nonequilibrium between electrons and the lattice consisting of neutrals and ions.