Alkali niobate and tantalate glasses have been prepared by rapid quenching. These glasses exhibit room‐temperature ionic conductivities as high as 10−5(&OHgr; cm)−1and electronic conductivities less than 10−11(&OHgr; cm)−1. In the case of LiNbO3, the glass conductivity is many orders of magnitude greater than that of the single crystal. These conductivities are sufficiently high for rapidly quenched vitreous oxides to be considered for applications as solid electrolytes.