Of the hundreds of Persian manuscripts preserved at The Institute of Ismaili Studies, many have long remained unknown or little studied. This open-access volume presents the first comprehensive catalogue of the Ismaili texts in this important collection, bringing previously inaccessible sources to light and opening new avenues of research in Ismaili studies and the study of the Iranian world. The catalogue introduces a range of hitherto unidentified authors central to the Ismaili history of the Iranian lands accompanied by concise biographical sketches. Each manuscript is described in detail, with information on provenance, scribes, and related codicological features, offering much-needed insight into these primary sources. The entries are organised in two main sections: the first devoted to monographs (single, titled works), and the second to anthologies of miscellaneous texts bound together, or majmu?as. In total, 126 manuscripts are examined, spanning a broad historical arc from the Fatimid period—including works associated with the renowned Ismaili philosopher and theologian Na?ir-i Khusraw—through to the modern era following the nineteenth-century migration of ?asan ‘Ali Shah, Aga Khan I, from Iran to India. The volume is enriched by a substantial introduction, along with carefully prepared tables and indexes that enable readers to locate specific works and authors with ease. Together, these features make the catalogue an indispensable resource for specialists in Ismaili and broader Islamic studies, while also offering non-specialist readers a clear and engaging overview of an extraordinary manuscript collection. The ebook editions of this book are available open access under a CC BY-NC-ND 4.0 licence on bloomsburycollections.com. Open access was funded by The Institute of Ismaili Studies