Magnesium (Mg2+) has many physiological functions within the body. These include important roles in maintaining cardiovascular functioning, where it contributes to the regulation of cardiac excitation–contraction coupling, endothelial functioning and haemostasis. The haemostatic roles of Mg2+impact upon both the protein and cellular arms of coagulation. In this review, we examine how Mg2+homeostasis is maintained within the body and highlight the various molecular roles attributed to Mg2+in the cardiovascular system. In addition, we describe how nutritional and/or disease-associated magnesium deficiency, seen in some metabolic conditions, has the potential to influence cardiac and vascular outcomes. Finally, we also examine the potential for magnesium supplements to be employed in the prevention and treatment of cardiovascular disorders and in the management of cardiometabolic health.