The development of novel anode materials with superior electrochemical performance is imperative for advancing next-generation high-performance rechargeable batteries beyond current limitations. In this study, it presents a 2D o-Al₂C₂ monolayer as a promising lightweight candidate for lithium and sodium–ion battery systems, based on the density functional theory investigations and ab initio molecular dynamics (AIMD) simulations. Our comprehensive investigation demonstrates that the o-Al₂C₂ monolayer exhibits remarkable stability with a cohesive energy of −5.30 eV atom⁻¹ and maintains its structural integrity at room temperature during extended AIMD simulations. The o-Al₂C₂ monolayer demonstrates exceptional electrochemical characteristics for Li and Na storage: theoretical specific capacities of 3780.42 and 3436.75 mA h g⁻¹, optimal average open circuit voltages of 0.81 and 0.67 V, and favorable diffusion barriers of 0.62 eV and 0.31 eV, respectively. These performance metrics significantly surpass those of conventional graphite (372 mA h g⁻¹) and other recently reported 2D anode materials, establishing o-Al₂C₂ as an exceptionally promising candidate for next-generation energy storage applications. Hence, this current theoretical investigation suggests that the o-Al₂C₂ monolayer holds significant potential for future experimental studies in lithium and sodium storage applications for LIB and NIB systems.