Theotokos is a Greek word that means "God-bearer" or "Mother of God". It is a title assigned by the early Christian Church to Mary, the mother of Jesus, at the Third Ecumenical Council held at Ephesus in 431. The theological significance at the time was to emphasize that Mary's son, Jesus, was fully God, as well as fully human, and that Jesus' two natures (divine and human) were united in a single person of the Trinity. The competing view at that council was that Mary should be called Christotokos instead, meaning "Mother of Christ". This was the view advocated by Nestorius, then Patriarch of Constantinople. The intent behind calling her Christotokos was to restrict her role to be only the mother of "Christ's humanity" and not His Divine nature.

Nestorius' view was anathematised by the Council as heresy, (see Nestorianism), since it was considered to be dividing Jesus into two distinct persons, one who was Son of Mary, and another, the divine nature, who was not. It was defined that although Jesus has two natures, human and divine, these are eternally united in one personhood. Mary being mother of God the Son is therefore duly entitled Mother of God.

Calling Mary the "Mother of God" was never meant to suggest that Mary was coeternal with God, or that she existed before Jesus Christ or God existed. The Church acknowledges the mystery in the words of this ancient hymn: "He whom the entire universe could not contain was contained within your womb, O Theotokos."

The title "Theotokos" continues to be used frequently in the hymns of the Eastern Orthodox and Oriental Orthodox churches.

See also

• Blessed Virgin Mary
• Immaculate Conception
• Our Lady of Vladimir
• Christology