The State is one of the central concepts of the contemporary international legal system: it is omnipresent in international legal scholarship and practice. Direct references to the system’s subject legislators are ubiquitous, but perhaps even more significant are the innumerable indirect references made to the idea by way of the multitude of concepts which allude to or draw meaning from it. In these ways the concept of the State structures the international legal system, and three of those structural functions are discussed in this chapter: personification, delineation and identification. The chapter argues that these functions, operationalized by international lawyers, define the limits of the international legal system’s reality, transforming fluid sociopolitical processes into a legal ‘truth’ which exists in a conceit of timelessness. In so doing, the concept of the State (to borrow from Giddens) both enables and constrains the international legal system.