Abstract: Infectious diseases have been spreading rapidly across the globe, posing serious impacts on human health and the global economy. At present, the long-term use of antiviral drugs is accompanied by issues such as drug resistance and adverse reactions. Therefore, developing novel antiviral agents is particularly important. Selenium is an essential trace element for humans and animals. Individuals or animals with low selenium levels are more susceptible to viruses, which can lead to more severe illnesses. In the prevention and treatment of viral infections, selenium exerts antioxidant activity, regulates the immune system, protects the stability of endothelial cells, and participates in the regulation of signaling pathways. The correlation between selenium and infectious diseases has attracted considerable attention. This article reviews the antiviral mechanisms of selenium, new antiviral targets of selenium, and the current methods of selenium supplementation, aiming to provide new ideas and medication approaches for the prevention and treatment of viral diseases.