Byline: Andrew Phillips, J. C. Sharman International Relations theories generally hold that increased interaction between units in an international system produces convergence in their forms through military competition, institutional emulation, or normative socialization. In contrast, we argue that diverse international systems can endure despite increasing interaction. The early modern Indian Ocean international system hosted a variety of statist, corporate, and imperial polities. Diversity endured for three reasons. First, powerful foreign and local actors held differing maritime and land-oriented preferences for conquest, which created the potential for coexistence between unlike polities. Second, congruent European and Asian ideas of heteronomy facilitated durable polity diversity. Third, strategies of localization enhanced enmeshment. Convergence on common polity forms failed to occur despite the presence of a statist model during this period. Subsequently, a reconfigured form of diversity under colonial empires succeeded this order. Greater attention to past diverse systems coheres with recent calls to study history to better understand not only contemporary instances of international hierarchy, but also unbundled and shared sovereignty regimes. Article Note: Author's notes: The authors are grateful for the invaluable feedback provided in response to earlier drafts of this work by Amitav Acharya, Charles Butcher, Alex Cooley, Luke Glanville, Ryan Griffiths, Seb Kaempf, Peter Katzenstein, Manjeet Pardesi, Chris Reus-Smit, Hendrik Spruyt, Shogo Suzuki, William Thompson, Wes Widmaier, three anonymous reviewers, and the editors of ISQ. The authors would also like to gratefully acknowledge the financial support of Australian Research Council Grants DE130100644 and FT120100485.