The Transdisciplinary Pathways for Sustainable Water Governance (TRANSWATER) project, implemented by researchers from UMR G-EAU (www.g-eau.fr), proposes to develop and test a framework to understand –and enhance- the ways transdisciplinary arrangements of coproduction can contribute to sustainable transformations of water governance in four hydrosocial territories. TRANSWATER aims to link recent interdisciplinary advances in water research and Sustainability Science’s commitment towards transformations while being attentive to the situated and contingent nature of research, hence contributing to the emergence of a reflexive Sustainability Science of Water. The project will be implemented in four hydrosocial territories where UMR G-EAU has on-going partnerships with a diversity of water actors: the greater Montpellier area in the South of France, the Lac de Guiers area in Senegal, groundwater-based agro-ecosystems in the south of Tunisia, and the Cambodian Upper Mekong delta. Recognizing that hydrosocial transformations are best assessed and brought about over the long term, we make the methodological choice to establish synergies with existing transdisciplinary processes that aim at identifying and implementing just and sustainable transformations in these hydrosocial territories. Grounded in what we call a “negotiated reflexivity” approach, the framework developed under the project will investigate the daily practices of designing and implementing these transdisciplinary processes while also generating new water knowledge. We expect this will yield insights of operational value to steer on-going transformations towards more just and sustainable ends in these four hydrosocial territories but also (1) generic lessons on how and why hydrosocial transformations come about and a (2) reflexive assessment of the role researchers at the science-action interface can play in these.