Nestorius, a well-known theologian and priest, was appointed as the Patriarch of Constantinople, succeeding the late Patriarch Sisinnius. His election to this influential religious position was supported by a faction within the church that valued his interpretations of Christian doctrine. Nestorius had previously made a name for himself with his teachings about Christology, particularly concerning the nature of Christ and the relationship between his divine and human aspects.

Upon taking office, Nestorius quickly became embroiled in theological controversy due to his views, particularly his opposition to the title Theotokos ('God-bearer') for the Virgin Mary, which he argued was misleading. He promoted the use of the term Christotokos ('Christ-bearer') instead. This theological stance sparked significant debate within the church and among theologians, leading to greater division between various Christian factions.

His tenure as Patriarch saw rising tensions with other early church leaders who disagreed with his Christological views, most notably Cyril of Alexandria. The disagreements regarding Christ's nature exemplified the difficulties faced by early Christianity as it sought to define its beliefs and solidify its doctrines in the face of diverse interpretations. Nestorius's tenure would eventually lead to greater schism, and his legacy continued to influence the development of non-Chalcedonian Christianity.