The chapter details early medieval riverine infrastructure, looking at ways that medieval leaders and communities understood the challenges and opportunities posed by the many rivers that supported and surrounded them. Working across the broadest range of sources, this chapter is the most focused on material culture and human infrastructure. It surveys practical responses, economic solutions, concerns about riverine sustainability, and the construction and maintenance of infrastructure (canals, mills, fish weirs, bridges, etc.), presenting the ways that medieval people responded to rivers on a daily basis. It also includes discussion of the regulation of riverine resources and the conflicts that could arise over rivers, ultimately arguing that rivers were actively contested, constructed, and integrated into the full economy, culture, and experience of medieval Europe.