Flooding is the most pervasive and costly natural hazard regularly faced by society. Extreme floods constitute significant agents of physical change on portions of the Earth's surface and leave diagnostic imprints in the geologic record, both ancient and recent. Most large floods result from the integrated effects of complex, multi-scaled interactions in Earth's atmosphere. Flood records from gaging stations typically have insufficient length to adequately characterize the actual temporal context of hydrologic extremes like large floods. The foregoing statements have a common theme—paleoflood hydrology—an interdisciplinary scientific method of reconstructing the history of flooding on rivers and streams from the basis of physical evidence of flooding. From a societal perspective, paleoflood hydrology provides a direct record of the types of floods that are most likely to cause the greatest damage. As a result, flood plain managers and regulatory agencies should benefit greatly from the research and interpretations that paleoflood hydrology offers.