GSTM3 (Glutathione S-Transferase Mu 3) is a gene that encodes an enzyme from the glutathione S-transferase family, which helps detoxify harmful compounds. It plays a crucial role in metabolising carcinogens, drugs, and byproducts of oxidative stress. Variations in GSTM3 may affect individual susceptibility to cancer, neurodegenerative diseases, and other conditions linked to detoxification pathways.