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