This paper considers the sense in which the increasingly global nature of economic, social, and political interaction influences the moral obligations that individuals have to foreigners. I defend a view called "global institutionalism", according to which individuals worldwide have duties of justice to one another in virtue of these forms of global interaction. The two main forms of criticism that confront global institutionalism come from opposing perspectives. On the one hand, "non-institutionalists' deem facts about global institutional interaction to be irrelevant for the purpose of determining the nature of our duties to others. They worry that many needy individuals will be excluded from our moral radar by grounding claims of justice on a morally arbitrary factor like institutional membership. "Domestic institutionalists", on the other hand, accept that interaction has significant bearing on the scope of justice but deny that the right sort of interaction necessary to ground duties of justice is found in the global domain. Against these objections, I defend the global institutionalist position by showing why it is the case that global interaction gives rise to new duties of justice that are irreducible to universal duties; moreover, I reveal the inconsistency of the domestic institutionalist position, which maintains a stark dichotomy in the moral commitments we have to compatriots and to foreigners in the face of extensive cross-border interaction. The successful defense of this thesis means that as global interdependence increases, we must re-think what we owe to those who reside beyond the borders of our own states.