The hypothesis that mountains influence global climate through links among rock uplift, physical and chemical denudation, and the carbon cycle remains vigorously debated. We address the contribution of mountains to global denudation with an empirical model that predicts that >50% of the total denudation and 40% of the chemical denudation occur on the steepest ∼10% of Earth’s terrestrial surface. These findings contrast with those from a recent study that suggested global-scale denudation occurs primarily on gently sloping terrain, but did not account for the influence of digital elevation model resolution on modeled denudation rates. Comparison of calculated denudation rates against the sum of measured sediment and solute yields from 265 watersheds indicates a positive correlation (R2 = 0.44) with order-of-magnitude variability reflecting, among other things, the effects of dams and agriculture. In addition, ratios of measured river yield to modeled denudation rate decline as catchment area increases due to progressively greater sediment storage with increasing drainage area. Our results support the conclusion that the small mountainous fraction of Earth’s surface dominates global denudation and the flux of sediment and solutes to oceans.