The belief that Mary is the Mother of God is a prominent doctrine within the Catholic Church. The specific reference to Mary as the Mother of God is not found in a single verse or chapter of the Bible, but rather it is based on a combination of biblical passages and theological interpretation.

The term "Mother of God" or "Theotokos" (Greek for "God-bearer") is used to affirm that Mary, as the mother of Jesus, gave birth to the Son of God who is fully divine and fully human. This belief has its roots in the early Christian Church and was officially recognized and affirmed at the Council of Ephesus in 431 AD.

While there isn't a single verse that explicitly states "Mary is the Mother of God," there are passages in the Bible that support this belief. One notable passage is Luke 1:43, where Elizabeth, filled with the Holy Spirit, exclaims to Mary, "And why is this granted to me that the mother of my Lord should come to me?" (ESV). This verse highlights the acknowledgment of Mary as the mother of the Lord, signifying her role as the mother of Jesus, who is God incarnate.

Additionally, other verses such as Luke 1:35 and Matthew 1:23 affirm the divine nature of Jesus and the fulfillment of Old Testament prophecies that the Messiah would be born of a virgin.

It is important to note that beliefs and doctrines within Christianity, including the role of Mary, can vary among different Christian denominations. The recognition of Mary as the Mother of God is particularly emphasized in Catholic theology and devotion.