Little theoretical attention has been paid to the question of what obligations corporations and other business enterprises have to the four billion people living at the base of the global economic pyramid. This article makes several theoretical contributions to this topic. First, it is argued that corporations are properly understood as agents of global justice. Second, the legitimacy of global governance institutions and the legitimacy of corporations and other business enterprises are distinguished. Third, it is argued that a deliberative democracy model of corporate legitimacy defended by theorists of political CSR is unsatisfactory. Fourth, it is argued that a Rawlsian theoretical framework fails to provide a satisfactory account of the obligations of corporations regarding global justice. Finally, an ethical conception of CSR grounded in an appropriately modest set of duties tied to corporate relationships is then defended. This position is cosmopolitan in scope and grounded in overlapping arguments for human rights.