Much of the terrestrial surface of our planet is sloping. Rivers and glaciers occupy some of this terrain, but the vast majority of sloping grounds are hillslopes, or simply “slopes.” Slope processes are those that generate and transport soil or regolith. Both chemical and physical weathering occurs on and within slopes, and mass transport can be rapid and hazardous, as in the case of mass wasting, or gradual, as in the case of soil creep. Although humans have presumably pondered since prehistoric times why landscapes look the way they do, the formal study of slope processes has its roots in the 19th century, when scientists began debating how sediment is produced, the mechanisms and rates at which it is transported, and the manner in which sloping lands evolve through time. The field of slope processes continues today with the aim of predicting socially relevant phenomena such as slope failure and soil sustainability. Recent advances have been abetted by new techniques allowing unprecedented accuracy in characterizing the topography, chemistry, material properties, ages, and transport rates of sloping landscapes.