The salient role of some notable Arab Ismailis in promoting the Fatimid mission and state in North Africa has received scholarly attention. Among these figures are the Fatimid scholar and chief justice q??? Ab? ?an?fa al-Nu?m?n [d. 363/974], Fatimid governors such as al-?asan b. ?Al? al-Kalb? [d. 356/956], and Ja?far b. ?amd?n [d. 370/980], and the Fatimid court poet Ibn H?ni? al-Andalus? [d. c. 362/973]. Nonetheless, studies on the role of Arab Ismailis as a broader collective in the Fatimid realms remain scant. Building on earlier studies on Fatimid state-society relations, this paper explores Arab Ismailis as a distinct social group who performed vital functions in the genesis and consolidation of Fatimid rule in North Africa, and in the broader struggle of legitimisation between Fatimid and Umayyad rule. Through a study of key figures as well as three principal Arab Ismaili clans of the early Fatimid period– the Ban? Ab? Khinz?r, the Ban? ?amd?n, and the Ban? Abi?l-?usayn al-Kalb?, the paper situates Arab Ismailis as key facilitators of Fatimid governance, and as mediators of Fatimid legitimisation, in the formative decades of the Fatimid Caliphate. This role of the Arab Ismailis was especially important in areas of rival political and religious loyalties, namely in Arab urban centres including Qayraw?n and Palermo, as well as in the frontier regions of the Fatimid empire. The paper also maintains that the importance of Arab Ismailis in performing such roles rendered them subject to the protracted struggle between the Fatimids and the Umayyads, in which they became targets of polemic, subterfuge and alliance. The paper begins by contextualising the notion of ‘Arabness’ as a medium of legitimisation in Fatimid North Africa, and as a node of rivalry between the Fatimids and the Umayyads. The social and political cache of Arab identity is subsequently situated as the charismatic feature upon which the careers of the key Arab Ismailis of the early Fatimid era were predicated. The role of Arab Ismailis examined in this paper, demonstrates that Fatimid state formation extended beyond ethnic and religious rivalries, drawing upon the spectrum of the Ifr?qiyan populace. Notably, this notion appears to have infused the da?wa that led to the promulgation of the Fatimid Imamate.