The Mekong River is one of the great rivers of the world and is characterized by high fish biodiversity. A number of organizations are working at observing and protecting aquatic biodiversity in this hotspot of global importance. Among them are international organizations such as the WWF, Wetlands International, the International Union for Conservation of Nature (IUCN), and the United Nation Environment Program (UNEP) but also regional institutions and national line agencies or nongovernmental organizations (NGOs). We review in this chapter the activities of fi ve international, regional, and national organizations involved in Mekong fi sh biodiversity research. These organizations include The WorldFish Center, Conservation International (CI), The Mekong River Commission (MRC), Ubon Ratchathani University, and the Japan National Institute for Environmental Studies (NIES). For each institution, we detail recent projects, modes of operation, issues faced, and priorities for improved observation and protection of biodiversity.