How did the Fatimids claim descent from Fatimah and Ali?

The Fatimid dynasty derived its name from Fatimah, the daughter of the Prophet Muhammad, and claimed legitimacy through direct descent from her and her husband, Ali.1

As leaders of the Ismaili sect of Shi'i Islam, the Fatimids maintained that their authority was established both by this lineage and by divine choice. They viewed themselves as the rightful imams—the spiritual successors to the Prophet—and rejected the Abbasid caliphs as usurpers. This claim of descent was central to their identity as the true custodians of the Islamic faith and the legitimate heads of the universal Islamic state. In 899, the movement's leader, Abd Allah, formally proclaimed this Ismaili imamate, explicitly linking his ancestry to the Prophet through Fatimah.12