Australian dryland rivers take many forms, provide critical ecosystem services, and are threatened by continued aridification as generally less rainfall and more evapotranspiration occur under changing climates. We defined the contemporary hydroclimatic controls on Australian dryland river geomorphology using available observational data from 29 catchments in eastern and central Australia, and then modelled the effect of greater future catchment aridity on alluvial river response. Enhanced aridification by 2070 (RCP4.5) will likely lead to major shifts in river morphology (i.e. channel size, shape and pattern related to flow and sediment transport) for 80% of the rivers assessed, with some systems experiencing a step-change from continuous channels to discontinuous and even terminal channels. The propensity for a transition towards discontinuous river types will have significant effects on downstream reaches and other systems reliant on through-going rivers, as well as dryland river ecology, desert refugia, and other unique ecosystem services, more generally. Climate-driven hydrological and geomorphological changes are therefore central to understanding the likely long-term future states of dryland rivers in Australia and around the world.