Al-Mu'ayyad fi l-Din al-Shirazi (1000–1078 CE) was an 11th-century Isma'ilism scholar, philosopher-poet, preacher and theologian of Persian origin. He served the Fatimid Caliph-Imāmal-Mustansir Billah as a Da'i in varying capacities, eventually attaining the highest rank of Bab al-Abwab "The Gate of Gates" and Da‘i al-Du‘at "Chief Missionary" in the Fatimid Da‘wah. In his theological and philosophical writings he brought the Isma'ili spiritual heritage to its pinnacle.
During the reign of the Fatimid Caliph-Imam Ali az-Zahir, Hibatullah ibn Musa was permitted to take over the da'wah office from his father. His title, Al-Mu'ayyad fi d-Din "The one aided in religion", was probably accorded to him around this time.
Hibatullah gradually worked his way up the hierarchy of the da‘wa and was eventually appointed Chief Missionary under the Caliph-Imam al-Mustansir Billah. In this position, he worked at the Dar al-'Ilm "House of Knowledge" teaching missionaries from both inside and outside the Fatimid Empire and composing his theological works until the end of his life in 1078 CE.
The primary source for details of al-Mu'ayyad's life are his own memoirs, the Sirat al-Mu'ayyad fi d-Din, which was written in three stages between the years 1051 and 1063 CE. He is also mentioned in the works of Nasir Khusraw, another prominent Isma'ili scholar of the time, who had learned under al-Mu'ayyad.
Majalis ul-Muayyadiyah - Written between 450 AH to 470 AH. Comprising eight volumes, each one hundred lectures. It deals with various theological and philosophical questions asked by people of other religions and atheists.
Diwan ul-Muayyad, a collection of poems in praise of the Ismai'ili Imams and the doctrines of their faith
Verena Klemm (2003). Memoirs of a Mission: The Ismaili Scholar, Statesman and Poet, al-Mu’ayyad fi’l-Din al-Shirazi. Ismaili Heritage Series 9, London: I. B. Tauris in association with The Institute of Ismaili Studies. ISBN978-1-86064-432-0.
Tahera Qutbuddin (2005). Al-mu'ayyad Al-shirazi And Fatimid Da'wa Poetry: A Case Of Commitment In Classical Arabic Literature. Brill Academic Publishers. ISBN978-90-04-14103-2.