The use of ammonia as a hydrogen carrier has received much attention due to its high hydrogen content and liquid state under mild conditions, which could lead to fuel cell applications. This study demonstrates facile ammonia decomposition on ruthenium nanoparticles loaded on inorganic electride, C12A7:e⁻. A high turnover frequency (∼12 s⁻¹ at 400 °C) and low activation energy (64 kJ mol⁻¹) for recombinative N₂ desorption were obtained for Ru/C12A7:e⁻. N₂-temperature programmed desorption (N₂-TPD) and kinetic analyses indicate that the high catalytic performance is due to the low work function of chemically stable C12A7:e⁻, which enables electron injection to the antibonding orbital of the Ru–N bond formed transiently through the reaction by raising the Fermi level of Ru metal.