This chapter examines the transition from state-led hydrocracies to increasingly liberalized modes of water resources development in mainland Southeast Asia, with a focus on large hydropower dams on transboundary rivers. Access to, use of and control over water is highly politicized, and an increasingly diverse assemblage of public, private and civil society actors are involved in water governance. The region’s major rivers, including the Irrawaddy, Salween, Mekong and Red Rivers, are simultaneously seen as: engines of national and regional economic growth via hydropower and irrigated agriculture; the foundation of rural livelihoods; of significant conservation value; and as cultural cornerstones/ sacred places. The chapter shows that trends in the use of water resources cannot be decoupled from broader trends towards regional economic integration, industrialization and economic growth, and that ecosystems and biodiversity are under increasing pressure, as are the rural livelihoods that depend upon these resources. The chapter argues that whilst state agencies with water-related mandates remain important, the interests of the private sector are of growing influence, especially for large hydropower dams. The chapter concludes that as electricity and water governance are increasingly intertwined, poor transparency and accountability in electricity planning represents a significant challenge to improving water governance outcomes.