Severe acute respiratory syndrome coronavirus type 2 (SARS‐CoV‐2) causes coronavirus disease 2019 (COVID‐19), characterised by high levels of inflammation and oxidative stress (OS). Oxidative stress induces oxidative damage to lipids, proteins, and DNA, causing tissue damage. Both inflammation and OS contribute to multi‐organ failure in severe cases. Magnesium (Mg
2+
) regulates many processes, including antioxidant and anti‐inflammatory responses, as well as the proper functioning of other micronutrients such as vitamin D. In addition, Mg
2+
participates as a second signalling messenger in the activation of T cells. Therefore, Mg
2+
deficiency can cause immunodeficiency, exaggerated acute inflammatory response, decreased antioxidant response, and OS. Supplementation with Mg
2+
has an anti‐inflammatory response by reducing the levels of nuclear factor kappa B (NF‐κB), interleukin (IL) ‐6, and tumor necrosis factor alpha. Furthermore, Mg
2+
supplementation improves mitochondrial function and increases the antioxidant glutathione (GSH) content, reducing OS. Therefore, Mg
2+
supplementation is a potential way to reduce inflammation and OS, strengthening the immune system to manage COVID‐19. This narrative review will address Mg
2+
deficiency associated with a worse disease prognosis, Mg
2+
supplementation as a potent antioxidant and anti‐inflammatory therapy during and after COVID‐19 disease, and suggest that randomised controlled trials are indicated.