Al-Azhar (The Luminous) was constructed as the central grand-mosque for Cairo by al-Qaid Jawhar al-Siqillí when he took Egypt for the Fatimid Imam-Caliph al-Mu‘izz li Dín Allah in 969 CE and founded Cairo as its capital city. It was inaugurated on 7 Ramadan 361 AH / 22 June 972 CE. Possibly so-named after Prophet Muhammad’s daughter Fatima al-Zahra, through whom the Fatimids traced their genealogy back to the Prophet.
Throughout the Fatimid period, al-Azhar played a vital role as one of the main mosques for the Imam-Caliph’s Friday prayers, where the Imam-Caliph himself often delivered the sermon; and also as an epicentre of religious learning.
via The Institute of Ismaili Studies – Al-Azhar: An Ancient Centre of Learning.