<p>Magnesium slag is a strongly alkaline industrial solid waste with a pH value exceeding 12. Its annual output reaches 8&#xa0;million tons, while the comprehensive utilization rate is less than 10%. Based on its active components (CaO, MgO, and C₂S), it can be transformed into seven functional materials for diverse applications, demonstrating significant economic and environmental benefits. This paper systematically reviews the sources, properties, and applications of magnesium slag in three key domains: environmental functional materials (catalysts, desulfurizers, and adsorbents), construction materials (cementitious materials and ceramics), and other materials (fertilizers and bifunctional material). The potential environmental risks in its application are discussed, current research gaps are clarified, and future research perspectives are outlined. Magnesium slag has exhibited remarkable potential for comprehensive utilization. Nevertheless, the factors restricting its large-scale application can be attributed to its low activity and inadequate stability. This review comprehensively summarizes the current research status of magnesium slag in diverse fields, aiming to provide theoretical basis and practical reference for promoting the resource and high-value utilization of magnesium slag.</p>