Gregory of Nyssa, also known as Gregory Nyssen (Greek: Γρηγόριος Νύσσης; c. 335 – c. 395), was bishop of Nyssa from 372 to 376 and from 378 until his death. He is venerated as a saint in Roman Catholicism, Eastern Orthodoxy, Oriental Orthodoxy, Lutheranism, and Anglicanism. Gregory, his elder brother Basil of Caesarea, and their friend Gregory of Nazianzus are collectively known as the Cappadocian Fathers.

Gregory lacked the administrative ability of his brother Basil or the contemporary influence of Gregory of Nazianzus, but he was an erudite theologian who made significant contributions to the doctrine of the Trinity and the Nicene creed. Gregory's philosophical writings were influenced by Origen. Since the mid-twentieth century, there has been a significant increase in interest in Gregory's works from the academic community, particularly involving universal salvation, which has resulted in challenges to many traditional interpretations of his theology.

This collection of the spiritual writings of St Gregory of Nyssa, selected and introduced by Jean Danielou, has long been recognized as an authoritative introduction to the 'father of mysticism,' who exploded classical antiquity's static understanding of perfection by showing the Christian life as one of never-ending growth, a true dynamic movement 'from glory to glory.' Modern thought has come more and more to appreciate the depth and insight of Gregory of Nyssa: he epitomizes, in a sense, all that is best in post-Nicean patristic thought... In Gregory's teaching of the sacred history of the story of God's dealings with men history and symbol fuse in a way that reveals all the uniqueness of the Christian message. Jean Danielou, from the Preface