The study investigates the mechanical performance of AZ31B magnesium alloy nanocomposites synthesized with varying weight percentages of zirconium dioxide (ZrO₂) nanoparticles using a stir casting process under an inert argon atmosphere. The aim is to improve the oxidation resistance and mechanical properties of the AZ31B alloy, which often suffer from porosity and reduced strength during die casting. The results show that the addition of ZrO₂ nanoparticles enhances the mechanical properties of the nanocomposites. Specifically, the composite containing 6 wt% ZrO₂ exhibited superior yield strength (212 ± 3 MPa), tensile strength (278 ± 2 MPa), and impact strength (16.4 ± 0.4 J/mm²). Additionally, the 8 wt% ZrO₂ blended composite showed the highest microhardness value (78.3 ± 1 HV). The best-enhanced result, NC3 (AZ31B/6 wt% ZrO₂), is recommended for lightweight to high-strength structural applications. The study also highlights the importance of uniform particle distribution and the optimal stir speed in achieving these enhanced mechanical properties.The study investigates the mechanical performance of AZ31B magnesium alloy nanocomposites synthesized with varying weight percentages of zirconium dioxide (ZrO₂) nanoparticles using a stir casting process under an inert argon atmosphere. The aim is to improve the oxidation resistance and mechanical properties of the AZ31B alloy, which often suffer from porosity and reduced strength during die casting. The results show that the addition of ZrO₂ nanoparticles enhances the mechanical properties of the nanocomposites. Specifically, the composite containing 6 wt% ZrO₂ exhibited superior yield strength (212 ± 3 MPa), tensile strength (278 ± 2 MPa), and impact strength (16.4 ± 0.4 J/mm²). Additionally, the 8 wt% ZrO₂ blended composite showed the highest microhardness value (78.3 ± 1 HV). The best-enhanced result, NC3 (AZ31B/6 wt% ZrO₂), is recommended for lightweight to high-strength structural applications. The study also highlights the importance of uniform particle distribution and the optimal stir speed in achieving these enhanced mechanical properties.