This is a study of transnational Shi'ism that explains the constitution of clerical leadership patterns across borders. Based on a political sociology of two families of religious scholars, al-Hakim and al-Khu'i, Elvire Corboz explains the internal workings of transnational leadership patterns in Shi'ism for the first time. Corboz compares the roles of Shi'i clerics in contemporary affairs with the traditional system of religious authority (the marja'iyya), political organisations and international charities. Whether informal or institutionalised, their authority networks are in constant negotiation between communities and states in Iraq, Iran, other Middle Eastern countries, the Indian sub-continent, South-East Asia and the West. It enhances our understanding of Muslim authority through a sociological analysis of the networking, philanthropic and political practices of Shi'i clerical actors across borders. It includes case studies of two prominent families of religious scholars (al-Hakim and al-Khu'i) to show the continued relevance of Shi'i clerics to Muslim politics and society. It deconstructs homogenising views of transnational Shi'ism by comprehending and localising cross-border religious networks in and beyond the Middle East.