This paper argues that historians have all but ignored the study of rivers and their impact on the development of human society. Apart from a somewhat terse acknowledgment of the importance of rivers in the development of ancient civilizations, from the Huang He to the Ganges, the Nile, and the Amazon, historians have by and large limited themselves to studying individual rivers, while ignoring the potential of comparative analysis of rivers. I call for a broader engagement by historians of all aspects of rivers, including their role in transportation, fishing, agriculture, industry, recreation, and the environment, peopled cultural response to rivers, and the legal regimes that have grown up around them, with special reference to the role of rivers as political boundaries.