Soils form at the interface between the atmosphere and Earth's surface through a complex combination of processes that vary in both time and space. Thus, soils also vary in space, and change with time. This time–space relationship allows us a valuable conceptual tool for deciphering and quantifying landscape evolution and the soil‐geomorphic history. Soils, surficial deposits, and landforms comprise three‐dimensional systems that coevolve. Accordingly, soils are geomorphic entities that vary with landform, substrate, hydrology, and slope position. In a geomorphic sense, we strive to understand the origin, distribution, and evolution of soils, landscapes, and surficial deposits, and the processes that create and alter them. Geologic/geomorphic processes substantially, but not solely, determine the materials from which soils form, insomuch as they determine the nature and distribution of sediments. This entry summarizes most of the major geomorphic principles and concepts used to understand the relationships among soils, landscapes, and surficial sediments, and pays special attention to hydrology as a driving factor in the soil‐landscape system.