Sudan, officially the Republic of Sudan, is a country in the north central part of Africa, just south of Egypt, that was influenced in antiquity by Egypt and later by the Roman empire. Sudan has known Christianity from the early centuries after Christ. Christianity reached Nubia, now northern Sudan, during the second century after Christ.
During the period of the Eastern Roman Empire Christian influence increased greatly under the jurisdiction of the Patriarch/Pope of Alexanderia.  Roman emperor Justinian I Nubia became a stronghold of Christianity. This influence is reflected in the Eastern Roman/Byzantine architecture of most of the Christian churches in lower Nubia  By 580, Christianity had become the official religion of northern Sudan, centered around the Faras cathedral.
After the Fourth Ecumenical Council at Chalcedon, the majority of the Church of Alexandria rejected the council's decrees and formed what is now generally known as the Coptic Orthodox Church (Oriental Orthodox) with a Pope/Patriarchate separate from that of the Church of Alexandria. Since the split into two jurisdictions, the majority of Orthodox faithful in the Sudan are members of the Coptic Orthodox Church of Alexandria (non-Chalcedonian) while a minor number are members of the Church of Alexandria (Chalcedonian).
After the Muslim conquests of the seventh century the Christian presence in Sudan slowly eroded as Muslim heirs came to ascendency among the ruling Nubian aristocracy. This caused a decline in Christian Nubia such that by the sixteenth century Muslims became in the majority. Today, the two Christian patriarchates are minority religions in the Republic of Sudan, with adherents living primarily in southern Sudan. Recent estimates places the number of "Greek" Christians at about 500 and "Coptic" at about 100,000. []
- Jakobielski, S. Christian Nubia at the Height of its Civilization (Chapter 8). UNESCO. University of California Press. San Francisco, 1992 ISBN 9780520066984