Metropolitan Bishop of Sardis in the context of Diocese of Asia

George Syncellus (Greek: Γεώργιος Σύγκελλος, Georgios Synkellos; died after 810) was a Byzantine chronicler and ecclesiastical official. He lived many years in Palestine (probably in the Old Lavra of Saint Chariton or Souka, near Tekoa) as a monk, before coming to Constantinople, where he was appointed synkellos (literally, "cell-mate") to Tarasius, patriarch of Constantinople. He later retired to a monastery to write what was intended to be his great work, a chronicle of world history, Ekloge chronographias (Ἐκλογὴ Χρονογραφίας), or Extract of Chronography. According to Anastasius Bibliothecarius, George "struggled valiantly against heresy [i.e. Iconoclasm] and received many punishments from the rulers who raged against the rites of the Church", although the accuracy of the claim is suspect.

As a synkellos, George stood high in the ecclesiastical establishment of Constantinople. The position carried no defined duties, but the incumbent would generally serve as the patriarch's private secretary, and might also be used by the Emperor to limit the movements and actions of a troublesome patriarch (as was the case during the reign of Constantine VI, when several of George's colleagues were set as guards over Patriarch Tarasius). The office would be an imperial gift by the time of Basil I, and was probably so earlier; as such, George may well have owed his position to the Empress Irene. Many synkelloi would go on to become Patriarchs of Constantinople, or Bishops of other sees (for example George's colleague, John, another synkellos under Patriarch Tarasius, who became Metropolitan Bishop of Sardis in 803).