Glutathione (GSH) is a vital antioxidant molecule found in cells, responsible for protecting against oxidative stress. However, research has shown that GSH has a much broader role in cellular signaling beyond its antioxidant activity. It plays a crucial role in regulating many cellular processes, including cell proliferation, differentiation, gene expression, and the immune response. As an antioxidant, GSH neutralizes free radicals, reactive oxygen species (ROS), and toxins that can damage cells and tissues. It also works closely with other antioxidants, such as vitamin C and E, to maintain cellular redox balance, preventing the development of oxidative stress-related diseases. GSH's role in cellular signaling is to control the activity of many enzymes and proteins by modifying their redox state. It can regulate the redox-sensitive molecules by donating electrons to them or by forming disulfide bonds that alter their activity, structure, and stability. For example, GSH activates some transcription factors responsible for the expression of antioxidant genes, and inhibits pro-inflammatory enzymes by reducing their activity. Additionally, GSH modulates various cytokines, chemokines, and growth factors, which are vital components of the immune system. It regulates the immune cell response by controlling the production and activity of these molecules, leading to a balanced immune response. Studies have shown that GSH enhances the proliferation and activity of T cells, which are crucial in fighting infections and cancer. GSH's role in cellular signaling is not only limited to its antioxidant and immune functions. It also regulates cell proliferation, differentiation, and apoptosis. GSH modulates the activity of several enzymes involved in DNA synthesis, repair, and replication, thus regulating cell cycle progression. Moreover, GSH promotes cell differentiation by activating specific signaling pathways and inhibiting others. Deficiencies in GSH levels have been linked to a variety of diseases, including cancer, neurodegenerative disorders, and metabolic diseases. GSH supplementation has been proposed as a therapeutic strategy to restore redox balance and improve cellular signaling in these diseases. In conclusion, GSH's role in cellular signaling is crucial and goes beyond its antioxidant function. This molecule regulates many cellular processes, including the immune response, cell proliferation, differentiation, and gene expression. Understanding the complex roles of GSH in cellular signaling can help in the development of new treatment strategies for a wide range of diseases.