This chapter presents a comprehensive review of transboundary human-water systems, emphasizing the coevolutionary dynamics that characterize these complex sociohydrological interactions. By adopting a co-evolving lens, the chapter elucidates the mechanisms through which phenomena such as conflict and cooperation arise within transboundary water systems. These phenomena are shown to be products of the intricate interplay between human activities and hydrological processes, influenced by both slow processes, such as long-term governance structures, and fast process, as hydrological variability. The forces shaping transboundary human-water systems, along with conflict and cooperation dynamics, can be better understood through multidiscipline, such as sociohydrology, peace and conflict studies, and political ecology. A critical examination of available datasets emphasizes the importance of these resources in modeling and understanding transboundary water and the necessity of rigorous data preprocessing and selection to ensure the consistency and validity of analytical outcomes. Four detailed case studies, each exemplifying different aspects of transboundary water management, are presented. The Eastern Nile River Basin case study illustrates the effects of the shifts in geopolitical power on cooperation. The Genevese Aquifer case study demonstrates the successful implementation of collective action for sustainable resource management. The Hueco Bolson/Valle de Juarez aquifer case study highlights the risks of overexploitation in the absence of coordinated governance. The Mekong River case study explores the complex and often asymmetric dynamics of conflict and cooperation driven by differential benefits among riparian states. The insights presented in this chapter offer valuable guidance for both scholars and policymakers seeking to understand and manage the challenges associated with transboundary water resources in an increasingly interconnected and dynamic global context.