Constitutional systems can be understood as a type of social (sub)system (Luhmann 1992). They have structures that contribute to the system’s own reproduction, maintain its status as a closed order, and mediate with external factors such as social and economic changes (Luhmann 1992: 1424-1425). These constitutional structures are sets of rules, principles, mechanisms, or procedures that allow constitutions to function, to continue existing over time, and to realise their purposes. Our aim in this chapter is to identify the different types of structures that tend to be present in contemporary constitutional systems, as well as the role they play in contributing to the purposes, continuing existence, and functioning of a constitution. We organise constitutional structures into six categories (limiting, enabling, preserving, change, power-sharing, and self-government structures). This analysis serves three important purposes. First, it provides content to the concept of 'constitutional structure,' which is frequently but sometimes loosely deployed by legal scholars. Second, it offers comparative constitutional lawyers and constitutional theorists a terminology through which they can describe certain important constitutional phenomena. Third, while being grounded in the internal operations of a constitutional system, our analysis underscores the need for interdisciplinarity in the study of constitutions, in light of the way constitutional structures interact with other systems.