AbstractMg−CO₂ battery has been considered as an ideal system for energy conversion and CO₂ fixation. However, its practical application is significantly limited by the poor reversibility and sluggish kinetics of CO₂ cathode and Mg anode. Here, a new amine mediated chemistry strategy is proposed to realize a highly reversible and high‐rate Mg−CO₂ battery in conventional electrolyte. Judiciously combined experimental characterization and theoretical computation unveiled that the introduced amine could simultaneously modify the reactant state of CO₂ and Mg²⁺ to accelerate CO₂ cathodic reactions on the thermodynamic‐kinetic levels and facilitate the formation of Mg²⁺‐conductive solid‐electrolyte interphase (SEI) to enable highly reversible Mg anode. As a result, the Mg−CO₂ battery exhibits boosted stable cyclability (70 cycles, more than 400 h at 200 mA g⁻¹) and high‐rate capability (from 100 to 2000 mA g⁻¹ with 1.5 V overpotential) even at −15 °C. This work opens a newly promising avenue for advanced metal‐CO₂ batteries.