The development of cost-effective, high-performance oxygen reduction reaction (ORR) electrocatalysts is pivotal for advancing energy conversion technologies such as metal–air batteries and fuel cells. Herein, we report a facile and efficient strategy to synthesize Mn nanoparticles loaded on N-doped hierarchically porous carbon framework (Mn/N-C) through utilizing ZIF-8 as a carbon/nitrogen precursor and MnCl₂·4H₂O as the Mn source. The synthesis integrates mechanical grinding with an NaCl-assisted pyrolysis process, where molten NaCl acts as a dynamic template and intercalation agent to prevent structural collapse during carbonization, thereby creating a 3D porous architecture with coexisting micro-, meso-, and macropores. Physicochemical characterization reveals that the Mn/N-C-2 sample exhibits a high specific surface area (1770 m²/g), abundant defects, and uniform dispersion of Mn nanoparticles within the N-doped carbon matrix. Electrochemical evaluations demonstrate that Mn/N-C-2 catalyst possesses a higher half-wave potential (E_1/2) of 0.836 V and a larger limiting current density (J_L) of 5.54 mA/cm², surpassing other control samples and most reported Mn-based catalysts and comparable to that of commercial Pt/C. When integrated into Zn–air batteries (ZABs), Mn/N-C-2-based ZABs deliver an open-circuit voltage of 1.49 V and a peak power density of 150.51 mW/cm², outperforming benchmark Pt/C-based counterparts. This work offers a cost-effective electrocatalyst for ORR and can be used instead of noble metals in ZABs.