Ismāʿīliyān-i Īrān is a study of the Ismailis of Iran., One of the most renowned and enigmatic branches of Islam is that of the Nizari Ismailis. This study starts from the fall of Alamut (654/1256) to the present day, with particular reference to the contemporary era. However, due to the Ismaili practice of precautionary dissimulation (taqiyya), outsiders remained unaware of the Ismailis, and thus, scarcely any mention of them appears in historical sources, except for occasional, fragmented, and often biased references. The following are a few of the questions posed by the author: How did they survive? What relationships did they establish with their neighbours? Did internal divisions or schisms occur among them? Whom did they recognise as their imams? In search of traces of the Nizari Ismaili community in Iran, the author visited the ruins of abandoned Ismaili fortresses, visited towns and villages, explored cemeteries, deciphered obscure inscriptions, and documented rock carvings. Caves and underground passages were investigated, and inquiries made among local people about groups who differed from the rest. This work endeavours to open a new window for researchers of Islamic history, those interested in religious communities and intellectual movements, as well as readers seeking a fresh perspective on one of the most mysterious intellectual and cultural currents in Iranian history.