<p>Flooding poses an increasing threat to lives and infrastructure worldwide, yet how river flow responds under climate change remains uncertain. Here we assess future changes in river hydrograph flashiness, defined as the rate of increase in streamflow normalized by time and drainage area, using a numerical hydrological model driven by multiple climate model projections. We analyze 520 major river basins globally. Results show that flashiness is projected to increase by about 14%, 30%, and 79% by the late twenty-first century under low-, intermediate-, and high-emission scenarios, respectively, relative to 2014. Increases are greater in low-latitude basins than in high-latitude regions. These changes are mainly associated with larger differences between peak and base flow and shorter times to reach peak discharge. Overall, our findings suggest that river floods are likely to become faster and more intense in a warming climate, posing growing challenges for flood risk management and infrastructure design.</p>