Energy‐storage systems are considered as a key technology for energy and mobility transition. Because traditional batteries have many drawbacks, there are tremendous efforts to develop so‐called postlithium systems. The magnesium–sulfur (MgS) battery emerges as one alternative. Previous studies of Mg–S batteries have addressed the environmental footprint of its production. However, the potential impacts of the use‐phase are not considered yet, due to its premature stage of development. Herein, a first prospective look at the potential environmental performance of a theoretical Mg–S battery for different use‐phase applications is given to fill this gap. By means of the life cycle assessment (LCA) methodology, an analysis of different scenarios and a comparison with other well‐established technologies are conducted. The results suggest that the environmental footprint of the Mg–S is comparable with that of the commercially available counterparts and potentially outperforms them in several impact categories. However, this can only be achieved if a series of technical challenges are first overcome.