The objective of the book is to analyze the Islamist and republican features of the political regime of the Islamic Republic of Iran. It aims to identify the relationship between Islamism and republicanism in terms of institutional and practical means throughout the period since the establishment of the Islamic Republic. The book tries to answer the question how the Islamist and republican orientations that built up the political regime and the system of governance in the Islamic Republic have affected the domestic political and ideological developments. After a discussion on the history of ulama-state relations and constitutional tradition, an analysis of emergence of Islamism and republicanism as indigenous ideological currents and the positions of political groups with respect to these two orientations are provided. Moreover, the institutional and practical implications of the coexistence of Islamist and republican orientations under the Islamic Republic and a current assessment of Islamism vs. republicanism debate in Iran are detailed inside the book.