The Mekong River has long conjured images of power: cascading waterfalls, impenetrable rapids, and pervading spirits. But power is always malleable and shifting, a fact not lost on the human and nonhuman agents who live with the river and its tributaries. Rises and drops in water levels that once fluctuated in accordance with the seasons have now become beholden to the electricity needs of urban centres like Bangkok: a shift from watershed to powershed. The emerging techno-political realities of the Mekong give rise to new ways of seeing and managing the river, often at the cost of longheld local understandings and configurations of power. The recent boom in hydropower development in the Mekong Basin has been alarming, and rapid change has had adverse impacts on the riparian peoples who depend on the river for their livelihoods. Despite the countless negative social and ecological impacts from dams, especially on the mainstream Mekong, hydropower investments and construction continue. New hegemonic scales and configurations of power have emerged in the Mekong Basin, but older local ones have not simply disappeared. Rather, power shifts in and out of plain sight. In this special issue, we trace the flows, scales, and reconfigurations of power from the management of Mekong water flows and the financing of hydropower projects through to the ruptures and (un) intended consequences of hydropower dam projects on living human and nonhuman worlds in the region. Through a multi-scaled and multi-sited lens, we bring to light emerging worlds in the Mekong Basin.