Mg alloys are important light structural materials and also are promising energy materials, which support Mg-based primary batteries such as Mg–air batteries as the main development direction of next-generation batteries. This rapidly developing field has attracted an increasing number of research investigations. We review the state-of-the-art of Mg-based anodes, including the fundamentals of Mg dissolution for primary batteries, the evaluation systems for the discharge performance of Mg-based anodes, the application of contemporary methods for understanding Mg discharge, and the influence of alloying and production methods. The recent developments, current opportunities and future directions of research are discussed. The main objective of this review is to help guide new studies that will promote the development of Mg-based anodes even further.