Landslides play a crucial role in the erosion and topographic evolution of active mountain belts. They drive the expansion of drainage networks in uplifting rock mass, and counter the tectonic mass flux into orogenic systems. Moreover, landslides are the source of most sediment eroded from the continents, and the probability distributions of landslides and their triggers are a first-order control on the variability of the sediment flux from active mountain belts. Here, we illustrate these points with observations from the Southern Alps and other regions of New Zealand, the Central Taiwan Mountains, the Finisterre Mountains of Papua New Guinea and the eastern Greater Caucasus of Azerbaijan.