Gregory of Nazianzus, also known as Gregory the Theologian or Gregory Nazianzen, was a 4th-century Archbishop of Constantinople, and theologian. He is widely considered the most accomplished rhetorical stylist of the patristic age. As a classically trained orator and philosopher he infused Hellenism into the early church, establishing the paradigm of Byzantine theologians and church officials.
Gregory made a significant impact on the shape of Trinitarian theology among both Greek- and Latin-speaking theologians, and he is remembered as the "Trinitarian Theologian". Much of his theological work continues to influence modern theologians, especially in regard to the relationship among the three Persons of the Trinity. Along with the brothers Basil the Great and Gregory of Nyssa, he is known as one of the Cappadocian Fathers.
Gregory of Nazianzus is a saint in both Eastern and Western Christianity. In the Catholic Church he is numbered among the Doctors of the Church; in the Eastern Orthodox Church and the Eastern Catholic Churches he is revered as one of the Three Holy Hierarchs, along with Basil the Great and John Chrysostom.