(Arabic: ست الملك, lit. ‘Lady of the Kingdom‘ ; 970–1023), was a Fatimid princess. After the disappearance of her half-brother, the caliph al-Hakim bi-Amr Allah, in 1021, she was instrumental in securing the succession of her nephew Ali az-Zahir, and acted as the de facto ruler of the state until her death on 5 February 1023.
She was born in September/October 970 at the palace-city of al-Mansuriya in Ifriqiya (modern Tunisia), to the prince Nizar—the future fifth Fatimid imam–caliph al-Aziz Billah (r. 975–996). Her mother was an unnamed concubine (umm walad), who is most likely to be identified with the al-Sayyida al-Aziziyya (“the Lady of al-Aziz”) who is frequently mentioned in the sources. She was a Melkite Christian, most likely of Byzantine Greek origin, possibly of the provincial aristocracy of Sicily who were captured in the wars against the Byzantines there sometime before 965. It is known that al-Sayyida al-Aziziyya refused to convert to Islam. Al-Aziz’s love for her was great, but scandalized pious Muslim opinion, especially at a time when al-Aziz was at war with the Byzantines in Syria; and reportedly caused suspicion that she was behind his tolerance towards Christians and Jews, which went as far as the appointment of a Christian, Isa ibn Nasturus, as vizier. In 986, two of her brothers were appointed to high office in the Melkite Church: Orestes became Patriarch of Jerusalem, and Arsenios was made metropolitan bishop of Fustat, and later Patriarch of Alexandria. It is still debated among modern scholars whether al-Sayyida al-Aziziyya was also the mother of Sitt al-Mulk’s younger brother, and al-Aziz’s heir and successor, al-Hakim bi-Amr Allah (r. 996–1021), but the evidence appears to be against it. When her mother died in November 995, the historian al-Maqrizi reports, Sitt al-Mulk held vigil at her tomb for one month. From her mother the princess inherited a slave girl, Taqarrub, who became her chief confidante and spy in the palace.