Solvated electrons in alkali metal-ammonia solutions have attracted attention as a prototype electronic conductor and chemical reducing agent for over a century. However, solvated electrons have not been realized in a high-temperature melt or glass of an oxide system to date. We demonstrated the formation of persistent solvated electrons in both a high-temperature melt and its glass by using the thermally stable electride [Ca24Al28O64](4+).4e(-)(C12A7:e(-)) and controlling the partial pressure of oxygen. The electrical and structural properties of the resulting melt and glass differ from those of the conventional C12A7:O2- oxide, exhibiting metallic and hopping conduction, respectively, and a glass transition temperature that is similar to 160 kelvin lower than that of C12A7:O2- glass. Solvated electrons reside in cage structures in C12A7:e(-) and form a diamagnetic paired state.