Nanocrystalline magnesium alloys having high tensile strength, high elevated-temperature tensile strength, high-strain-rate superplasticity and high thermal stability have been developed in Mg₉₇Zn₁Y₂ (at%) alloy by rapidly solidified powder metallurgy (RS P/M) processing. The tensile yield strength and elongation that were dependent on the consolidation temperature were in the ranges of 480 to 610 MPa and 5 to 16%, respectively. Young’s modulus of the RS P/M alloy was 45 GPa. The specific tensile yield strength was four times as high as that of a commercial AZ91-T6 alloy, and was higher than those of conventional titanium (Ti–6Al–4V) and aluminum (7075-T6) alloys. The RS P/M alloys exhibited excellent elevated-temperature yield strength that was 510 MPa at 423 K . The RS P/M alloy also exhibited high-strain-rate superplasticity at a wide strain-rate range from 1×10⁻² to 1×10⁰ s⁻¹ and at a low temperature of 623 K . It is expected that the Mg₉₇Zn₁Y₂ RS P/M alloy can be applied in some fields that requires simultaneously the high specific strength at ambient and elevated temperatures and high workability.