Glutathione Reductase (GR) is a key enzyme that maintains the reduced state within cells, protecting them from oxidative damage by reducing oxidized glutathione (GSSG) to reduced glutathione (GSH). Primarily located in the cytoplasm and mitochondria, GR is ubiquitous across all types of cells. It is involved in crucial biological reactions and signaling pathways, such as antioxidant defense, detoxification of toxins, and cell signaling. The gene expression level and activity of GR are regulated by a variety of environmental and intracellular factors. Mutations in the gene or aberrant expression can affect its enzyme activity, leading to a decreased capacity of cells to respond to oxidative stress, and are associated with a range of diseases including cardiovascular diseases, cancer, and neurodegenerative diseases.