S-Nitrosoglutathione (GSNO) is a biologically significant S-nitrosothiol formed by the covalent attachment of a nitric oxide (NO) moiety to the sulfur atom of the tripeptide glutathione (GSH). It serves as a stable, endogenous reservoir and transport form of nitric oxide in biological systems. GSNO is a key mediator of NO-related signaling pathways, influencing processes such as vasodilation, neurotransmission, and immune response. It functions as a transnitrosylating agent, transferring the NO group to other protein thiols, thereby regulating protein function and activity. In research, it is widely used as a tool compound to study NO biology, oxidative stress, and redox signaling. It is also investigated as a potential reference standard or metabolite in pharmacokinetic studies of NO-donor drugs. Due to its role in modulating vascular tone and platelet function, GSNO has been explored for therapeutic applications in conditions like cardiovascular diseases and pulmonary hypertension. It requires careful handling and storage under inert conditions (e.g., argon or nitrogen atmosphere) at low temperatures to prevent decomposition.