Constitutional theorists have had relatively little to say about the identity of what they study. This article addresses this inattention with a philosophical and comparative exploration of the concept of constitutional identity. Without such attention, a major preoccupation of theorists—constitutional change—will continue to be inadequately considered. The argument is advanced that there are attributes of a constitution that allow us to identify it as such, and that there is a dialogical process of identity formation that enables us to determine the specific identity of any given constitution. Representing a mix of aspirations and commitments expressive of a nation's past, constitutional identity also evolves in ongoing political and interpretive activities occurring in courts, legislatures, and other public and private domains. Conceptual possibilities of constitutional identity are, herein, pursued in two constitutional settings—India and Ireland—that highlight its distinctive features.