Riverscapes have recently gained renewed scholarly attention in historical, environmental, and cultural studies on man and the natural environment. This paper explores the extent to which the main rivers of the Southeast Asian subcontinent have given shape to the rice growing human societies that emerged in their basins and, further, how those rivers may have influenced distinct historical state formation processes. In Southeast Asian islands, riverscapes became the cradles of a completely different kind of state formation process: the estuary-based Malay port polity.