Iron-based nanostructures represent an emerging class of catalysts with high electroactivity for oxygen reduction reaction (ORR) in energy storage and conversion technologies. However, current practical applications have been limited by insufficient durability in both alkaline and acidic environments. In particular, limited attention has been paid to stabilizing iron-based catalysts by introducing additional metal by the alloying effect. Herein, we report bimetallic Fe₂Mo nanoparticles on N-doped carbon (Fe₂Mo/NC) as an efficient and ultra-stable ORR electrocatalyst for the first time. The Fe₂Mo/NC catalyst shows high selectivity for a four-electron pathway of ORR and remarkable electrocatalytic activity with high kinetics current density and half-wave potential as well as low Tafel slope in both acidic and alkaline medias. It demonstrates excellent long-term durability with no activity loss even after 10,000 potential cycles. Density functional theory (DFT) calculations have confirmed the modulated electronic structure of formed Fe₂Mo, which supports the electron-rich structure for the ORR process. Meanwhile, the mutual protection between Fe and Mo sites guarantees efficient electron transfer and long-term stability, especially under the alkaline environment. This work has supplied an effective strategy to solve the dilemma between high electroactivity and long-term durability for the Fe-based electrocatalysts, which opens a new direction of developing novel electrocatalyst systems for future research.