One of the prescriptions for adaptive comanagement of social-ecological systems is to follow a bioregional approach. In water resources management, experience has been gained with a bioregional approach by the foundation of river basin organizations (RBOs). Here, we summarize the results of a research project involving 27 colleagues who have undertaken an analysis of the global discussion on RBOs and the foundation of RBOs in Canada, USA, Great Britain, Germany, Portugal, South Africa, Ukraine, Afghanistan, Mongolia, Thailand, and Australia. Drawing on Ostrom's institutional analysis and development framework, we first present a fine-grained analysis of the institutional architecture of these RBOs, which enables us to distinguish between autonomous, coordinating, partnership, and agency type RBOs. Second, we unravel the main controversies over this architecture by focusing on the key actors involved in either promoting or hindering RBO formation, globally and at the national level. Third, we summarize how the performance of RBOs can be evaluated in terms of coordination, accountability, legitimacy, and environmental effectiveness. Finally, we discuss the relationship between institutional design and performance. The main findings are: (1) the foundation of RBOs is not a neutral process but rather a highly political one, (2) the foundation of RBOs creates complex accountability relationships, and (3) institutional interplay, the capacity to generate financial resources, and a minimum degree of institutional stability are crucial to the successes of RBOs in realizing coordination and environmental effectiveness.