Ubayd Allah al-Mahdi Billah
After establishing himself as the first Imam of the Fatimid dynasty he made claim to genealogic origins dating as far back as Fatimah, the daughter of the Prophet of Islam, Muhammad, through Husayn, Fatimah's son, and Ismail. It was at this time as well that he changed his name to Ubaydallah Al-Mahdi.