Orestes Hieremias (Greek: Ὀρέστης), also called Ariston,[1] was the Melkite Patriarch of Jerusalem from 15 January 986 until his death on 3 February 1006.
[5] He may be the monk whom the caliph sent to the Kalbid emir of Sicily, Ja'far ibn Muhammad al-Kalbi (r. 983–985) to secure the surrender of some Byzantine fortresses and prisoners previously captured by his grandfather Hasan.
[7] In 992, Orestes and Patriarch Elias I of Alexandria sent envoys to Pope John XV, reportedly to seek counsel on incorporating Monophysites into the church, at a time when the Byzantine Empire was expanding at the expense of the Arabs, and to receive the right to consecrate the altar cloth.
[10] Orestes' nephew, al-Hakim bi-Amr Allah, succeeded al-Aziz Billah in 996, but the first years of his reign were spent under the tutelage of the court eunuch Barjawan.
In 1000, in response to a previous Byzantine embassy, Barjawan sent Orestes to Constantinople to negotiate a ten-year peace treaty with the Emperor Basil II and end the Byzantine–Fatimid clashes in Syria.