Layered double hydroxide (LDH) nanosheets have exceptionally high hydroxyl ion (OH^-) conductivity (as high as 10^-1 S/cm), report investigators. This OH^- conductivity is 10 to 100 times higher than that of conventional OH^- conductors, and is the highest even among inorganic anion conductors. LDH nanosheets may be applicable as solid electrolytes for alkaline fuel cells and water electrolyzers, among other devices.