Ioannis Chryssavgis

John Chryssavgis (born 1 April 1958) is an Orthodox Christian theologian who serves as advisor to the Ecumenical Patriarch on environmental issues. He is a clergyman of the Greek Orthodox Archdiocese of America. In January 2012, he received the title of Archdeacon of the Ecumenical Throne by His All-Holiness Ecumenical Patriarch Bartholomew. In 2016, he was awarded an honorary doctorate by Saint Vladimir's Orthodox Theological Seminary. In 2020, he was elected Honorary Professor of Theology in the Sydney College of Divinity.

Early life and education John Chryssavgis was born in Australia in 1958. He matriculated from the Scots College in Sydney in 1975 and received his degree in theology from the University of Athens in 1980. He received a diploma in Byzantine Music from the Greek Conservatory of Music in 1979 and was awarded a research scholarship to St. Vladimir's Theological Seminary in 1982. He completed his doctoral studies in Patristics at the University of Oxford in 1983. Chryssavgis read patristic theology at Oxford.

Career His work and writing have focused on medieval theology, as well as on the history of the Eastern Church. He holds degrees in theology and sacred music. His teaching has covered wide-ranging topics, such as theological, political, and social developments, themes and personalities of the Middle Ages, including cultural and religious relations and tensions between East and West. His interests have embraced the areas of spirituality, ecology, and liturgy. His research is in the ascetic thought and practice of the early Church, especially from the desert tradition of Egypt (4th century) through the regions of Palestine (5th–6th centuries) and Sinai (7th century). After several months in silent retreat on Mount Athos, he worked with the Greek Orthodox Primate in Australia (1984–1994) and was co-founder of St Andrew's Theological College in Sydney, where he was Sub-Dean and taught Patristics and Church History (1986–1995). He was also Lecturer in the Divinity School (1986–1990) and the School of Studies in Religion (1990–1995) at the University of Sydney.

In 1995, he moved to Boston, where he was appointed Professor of Theology at Holy Cross School of Theology and directed the Religious Studies Program at Hellenic College until 2002. He established the Environment Office at the same school in 2001. He has also taught as professor of Patristics at the University of Balamand in Lebanon. Chryssavgis is a frequent contributor to the journal Public Orthodoxy published by the Orthodox Christian Studies Center of Fordham University.

Chryssavgis was appointed a Member of the Order of Australia in the 2026 King's Birthday Honours in recognition of his "significant service to the Orthodox Christian Church, to education, and to advancing ecological awareness".

He lives in Maine.