St. Gregory lived in the fourth century. A brilliant theologian and teacher, he was consecrated bishop of Nyssa by his older brother, St. Basil the Great.
Together the brothers fought against the Arian heresy, and suffered persecution by Arian clergy. More than once, St. Gregory was removed by his see by the Arians. He continued to teach, even wandering with his flock from place to place. He was restored as bishop of Nyssa in 378.
Gregory participated in the Second Ecumenical Council in 381, and was the driving force behind completing the Nicene Creed, adding the section about the Holy Spirit.
He reposed about the year 395, and his feast is celebrated on January 10. He was called "the Father of Fathers" by his contemporaries, and is one of the greatest theologians of the Church.