On the tenth of Muḥarram, in the 61st year of the hijra (October 10, 680), a grandson of the Prophet Muḥammad perished as a martyr on the banks of the Euphrates, amidst the arid plain of Karbalāʾ in southern Iraq. The death of al-Ḥusayn b. ʿAlī at the hands of Umayyad forces is an upsetting memory, chiefly for Shiites but more broadly for the Islamic community as a whole. This battle, frequently regarded by modern specialists as a relatively “minor” episode—often reduced, in fact, to a police operation directed against a rebel refusing to acknowledge caliphal authority—involved the death of a few dozen people (the sources most commonly speak of 70 or 72 victims), who were massacred by a significantly larger caliphal army. It rapidly became, however, a central event of early Islam and a foundational stone in the effort at articulating a narrative of the primordial Islamic past. As such, it generated highly ritualized annual commemorations to this day. Indeed, the central place of ʿĀshūrāʾ offers an obvious reminder of the importance and actuality of al-Ḥusayn’s memory for Muslims, as it includes most famously a reenactment of his martyrdom at Karbalāʾ in the form of taʿziya plays, as well as a variety of rituals, perhaps best exemplified by the (much-debated) practice of flagellation. But if the episode was intensely remembered and commemorated by a large number of Muslims, Karbalāʾ could also represent a challenge to other groups who endeavored to erase its memory. From this perspective, Karbalāʾ is clearly an Islamic lieu de mémoire to borrow from Pierre Nora’s terminology, that is, a site of memory sometimes contested precisely because of its actuality and ever-changing present-day relevance. It is therefore quite paradoxical that although this episode exemplifies the drama par excellence of early Islam, it has been so little studied by modern scholars, even if its modern developments have attracted more attention. This paper thus aims to investigate the conditions of historical knowledge of the Karbalāʾ episode and to trace its narrative crystallization during the first centuries of Islam. How was it remembered by some and forgotten by others? How was its memory constructed? In short, how was the historiographical vulgate of such a central event elaborated? As the most traumatic episode of nascent Islam, al-Ḥusayn’s martyrdom required the greatest historiographical effort and thus the details of the construction of its memory deserve scrutiny.