Since the Safavid period, Shi‘ism has become one of the enduring components of Iran’s political identity; however, this continuity has not been realized within an unchanged political structure. The main question of this study is: What aspects of Shi‘i identity have persisted in the Safavid state and the Islamic Republic, and how has its institutionalization within the structure of the state evolved? The study hypothesizes that, despite the continuity of Shi‘ism as a major source of political identity and legitimacy, its position within the state has shifted from a model in which Shi‘ism legitimized monarchy under the Safavids to one in which juristic authority has been institutionalized within the constitutional structure of the Islamic Republic. Employing a historical-comparative method and drawing on historical, legal, and relevant scholarly sources, the study compares the two periods in terms of the sources of political legitimacy, the position of the jurist, the relationship between religion and the state, and the political function of Shi‘i identity. The findings indicate that, under the Safavids, Shi‘ism became institutionalized within the political order while the Shah remained at the apex of power. In the Islamic Republic, by contrast, Shi‘i jurisprudential authority, through the institution of Velayat-e Faqih, has become part of the formal structure of sovereignty. Thus, the relationship between the two periods can be explained in terms of the continuity of Shi‘i identity alongside the transformation of state structure.