Abu'l-Qāsim al-Ḥasan ibn Faraj ibn Ḥawshab ibn Zādān al-Najjār al-Kūfī, better known simply as Ibn Ḥawshab, or by his honorific of Manṣūr al-Yaman, was a senior Isma'ili missionary from the environs of Kufa. In cooperation with Ali ibn al-Fadl al-Jayshani, he established the Isma'ili creed in Yemen and conquered much of that country in the 890s and 900s in the name of the Isma'ili imam, Abdallah al-Mahdi, who at the time was still in hiding. After al-Mahdi proclaimed himself publicly in Ifriqiya in 909 and established the Fatimid Caliphate, Ibn al-Fadl turned against him and forced Ibn Hawshab to a subordinate position. Ibn Hawshab's life is known from an autobiography he wrote, while later Isma'ili tradition ascribes two theological treatises to him.

Abū Muḥammad ʿAbd Allāh ibn al-Ḥusayn, better known by his regnal name al-Mahdī biʾllāh, was the founder of the Isma'ili Fatimid Caliphate, the only major Shi'a caliphate in Islamic history, and the eleventh Imam of the Isma'ili branch of Shi'ism.