AQP4, or Aquaporin-4, is a membrane protein predominantly expressed in the central nervous system, particularly highly concentrated in the end-feet of astrocytes. Belonging to the aquaporin family of proteins, AQP4 facilitates the rapid bidirectional movement of water molecules across cell membranes. This critical function is essential for maintaining water homeostasis in the brain, cerebrospinal fluid circulation, and normal neuronal function. AQP4 promotes the swift exchange of water between the intracellular and extracellular compartments, as well as among cells, playing a pivotal role in regulating the formation and resolution of brain edema. By modulating this process, AQP4 safeguards neurons from damage caused by edema. Furthermore, AQP4 is implicated in the pathological mechanisms of various neurological disorders, such as stroke, traumatic brain injury, epilepsy, and multiple sclerosis. In these conditions, alterations in AQP4 expression or function can disrupt brain water balance and impact neuronal survival.