Saint Gregory Nazianzen, also known as Gregory of Nazianzus, was a prominent early Christian theologian and one of the Cappadocian Fathers. Born around 329 AD in Nazianzus, he played a crucial role in the development of Christian doctrine, particularly concerning the nature of the Holy Trinity. He served as the Archbishop of Constantinople and was known for his eloquent sermons and writings. Gregory was a key figure at the First Council of Constantinople in 381 AD, where he defended the divinity of the Holy Spirit. His contributions to Christian theology and his advocacy for the Nicene faith helped shape the beliefs of the early Church. He is celebrated as a Doctor of the Church and is commemorated on January 2nd.