<p>The effects of Yb/Zr micro-alloying on the microstructure, mechanical properties, and corrosion resistance of an Al-Zn-Mg-Cu alloy were systematically investigated. Upon the addition of Yb/Zr to the Al-Zn-Mg-Cu alloy, the grain boundaries were pinned by high-density nanosized Al₃(Yb, Zr) precipitates during extrusion deformation, consequently, the average grain size was significantly reduced from 232.7 µm to 3.2 µm. This grain refinement contributed substantially to the improvement in both strength and elongation. The ultimate tensile strength, yield strength, and elongation of the Yb/Zr modified alloy increased to 705.3 MPa, 677.6 MPa, and 8.7%, respectively, representing enhancements of 16.2%, 19.3%, and 112.2% compared to the unmodified alloy. Moreover, the distribution of MgZn₂ phases along grain boundaries became more discontinuous in the Yb/Zr modified alloy, which effectively retarded the propagation of intergranular corrosion and improved the corrosion resistance.</p>