An attempt was made to develop a corrosion-resistant, high-strength Mg alloy using multi-directional forging (MDF). An extruded alloy as well as pure Mg was MDFed at temperatures between 220 and 340 °C with 40 °C intervals. Grains, second phase distribution, and Volta-potential difference between second phases and matrix were measured. Moreover, tensile and compression tests were used to assess mechanical properties. The corrosion behavior was characterized using electrochemical, hydrogen evolution, and mass loss techniques. A corrosion-resistant Mg alloy with a corrosion rate less than even high purity Mg obtained which has not been previously reported for a light Mg alloy. It was found that the lowest corrosion rate can be obtained for the alloy MDFed at 300 °C.