Hillslope runoff refers to the water flowing over the uplands of the earth during and after rain or following snow melt or glacier melt, either by overland sheet flow or channel in rills and ephemeral gullies. This chapter describes the hillslope runoff process and correspondingly hillslope soil erosion processes, including raindrop splash, sheet erosion, rill erosion, and ephemeral gully erosion. This chapter also introduces mathematical models of hillslope runoff, and empirically based and process-basede erosion models, and outlines mitigating and controlling hillslope soil erosion.