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Methane (CH<sub>4</sub>) is a potent greenhouse gas and its concentrations have tripled in the atmosphere since the industrial revolution. There is evidence that global warming has increased CH<sub>4</sub> emissions from freshwater ecosystems<sup>1,2</sup>, providing positive feedback to the global climate. Yet for rivers and streams, the controls and the magnitude of CH<sub>4</sub> emissions remain highly uncertain<sup>3,4</sup>. Here we report a spatially explicit global estimate of CH<sub>4</sub> emissions from running waters, accounting for 27.9 (16.7-39.7) Tg CH<sub>4</sub> per year and roughly equal in magnitude to those of other freshwater systems<sup>5,6</sup>. Riverine CH<sub>4</sub> emissions are not strongly temperature dependent, with low average activation energy (E<sub>M</sub> = 0.14 eV) compared with that of lakes and wetlands (E<sub>M</sub> = 0.96 eV)<sup>1</sup>. By contrast, global patterns of emissions are characterized by large fluxes in high- and low-latitude settings as well as in human-dominated environments. These patterns are explained by edaphic and climate features that are linked to anoxia in and near fluvial habitats, including a high supply of organic matter and water saturation in hydrologically connected soils. Our results highlight the importance of land-water connections in regulating CH<sub>4</sub> supply to running waters, which is vulnerable not only to direct human modifications but also to several climate change responses on land.