The Tustarī family was a prominent house of long-distance traders, bankers, courtiers, and scholars in Fatimid Egypt between the 990s and 1050s. Manuscripts from the Cairo Geniza and the Firkovich collections have permitted the reconstruction of the family’s history over four generations. More than sixty letters, contracts, and other documents in various Geniza collections attest to its close involvement with the leadership of the Jerusalem yeshiva and the Syrian synagogue of Fustat, even though, unlike the other great merchant houses of Ibn ʿAwkal, Tāhertī, and Nahray ben Nissim,…