A novel form of international order was developed in the nineteenth century by international administrative unions such as the International Telegraph Union and the Universal Postal Union. This administrative internationalism posed a striking alternative to the international society of great powers, sovereignty, and forms of imperial domination, for the members of administrative unions included not only sovereign states but also semi-sovereigns, vassals, and colonies. Members were equal and bound identically to the union treaty and its international administrative law. This article examines the structure of unions and their politics of membership in the nineteenth century, and engages theories of global governance to argue that early administrative unions present a mode of international order different from theories of both global networks and the international system of neorealism.