ABSTRACT. Since the mid-nineteenth century, historians have taken national states as the principal focus of their scholarship. Since the mid-twentieth century, they have increasingly recognized the importance of large-scale historical processes that transcend the boundaries of national states, and they have identified large-scale zones of interaction that help to bring these processes into clear focus. Sea and ocean basins show considerable promise as frameworks for the analysis of some historical processes. They would not serve well as the absolute or definitive categories of historical analysis because their contours and characteristics have changed dramatically over time with shifting relationships between bodies of water and masses of land. But they are especially useful for bringing focus to processes of commercial, biological, and cultural exchange, which have profoundly influenced the development of both individual societies and the world as a whole.