International shipwrecks were a geopolitical problem and opportunity in maritime Asia during the period of European discovery and colonization. This thesis argues that castaways were utilized by European and American interlopers in two main ways. First, castaways served as intermediaries and as sources of linguistic, geographic, cultural, and commercial information. In this way, even shipwrecks helped propagate new connections in imperial networks. Second, by framing the treatment and repatriation of castaways as a humanitarian issue in the nineteenth century, imperial states undermined the legitimacy of East Asian tributary networks and justified armed intervention. Finally, Japan's socialization into European International Society was marked by the adoption of Western shipwreck norms and the similar use of armed intervention for the protection of shipping routes. Castaways were an important component of the imperial tool-kit in maritime Asia.