Mg alloy is the lightest metallic structural material and possesses the advantages of high specific strength, high specific stiffness, good electromagnetism shield, good damping capacity, good machinability, and easy recycling, etc. Therefore, it has extremely broad application prospects and has drawn considerable interest in the fields of automobile, electronics, electrical appliances, transportation, aerospace, and aviation. In addition, Mg alloys are gradually showing application potential in emerging industries, serving as biodegradable metals in the biomedical field, functional material for hydrogen storage, and so on. This Special Issue (SI), entitled "Research Progress in High-Performance Magnesium Alloy and Its Applications", presents recent developments and excellent results in the field of Mg alloys, and includes 10 articles and one editorial covering some interesting aspects of the topic.