Reactive oxygen species (ROS) are widely recognized as intracellular signaling mediators and contributors to oxidative damage. Increasing evidence indicates that redox processes in the extracellular space constitute a distinct and functionally relevant layer of immune regulation. Extracellular ROS are generated in a spatially and temporally controlled manner by immune and non-immune cells and are shaped by local antioxidant buffering, redox-active metabolites, and tissue architecture. Rather than acting as diffuse by-products of inflammation, extracellular redox conditions modulate immune cell activation, migration, and intercellular communication by influencing surface-associated signaling events and receptor responsiveness. Physiological redox control in the extracellular compartment supports host defense, tissue repair, and coordinated immune responses. In contrast, disruption of spatial redox regulation promotes chronic inflammation, immune dysfunction, cancer-associated immune suppression, and systemic inflammatory states such as sepsis. Loss of redox confinement and insufficient extracellular buffering uncouple redox signaling from its regulatory function and contribute to endothelial dysfunction, immune dysregulation, and tissue injury. Together, these observations identify the extracellular redox balance as an integral component of immune regulation with important implications for understanding inflammatory pathology and for the development of strategies that preserve localized redox control rather than globally suppressing ROS.