The Oriental Orthodox churches came to a [[schism|parting of the ways]] with the remainder of [[Christianity]] in the 5th century. The separation resulted in part from the Oriental Orthodox churches' refusal to accept the [[Christology|Christological]] [[dogma]]s promulgated by the Council of [[Fourth Ecumenical Council|Council of Chalcedon]], which held that [[Jesus Christ]] is in two natures — one divine and one human, although these were inseparable. To the [[hierarch]]s who would lead the Oriental Orthodox, this was tantamount to accepting [[Nestorianism]]. In response, they advocated a formula that stressed unity of the [[Incarnation]] over all other considerations, that being "one nature of God the Word Incarnate", "of/from two natures" in and after the union. The Oriental Orthodox churches are therefore often called "[[Monophysitism|Monophysite]]" churches, although they reject this label, which is associated with [[Eutychianism|Eutychian Monophysitism]], preferring the term ''non-Chalcedonian'' or ''Miaphysite'' churches. Oriental Orthodox Christians anathematize the Monophysite teachings of [[Eutyches]]. They are sometimes also known as ''anti-Chalcedonians''.

The [[Assyrian Church of the East]] is sometimes considered an Oriental Orthodox Church, although it is not in communion with Oriental Orthodox churches and they have a [[Nestorianism|Nestorian]] or Nestorian-like [[Christology]] that differs from the declaration of the [[Fourth Ecumenical Council|Council of Chalcedon]] in an opposite way from the [[Miaphysitism|Miaphysites]]. By the time of the Monophysite controversy, the Assyrians had already separated from the Orthodox Church with the [[Third Ecumenical Council|Council of Ephesus]]. The Church follows the [[East Syrian Rite|East Syrian rite]].