Beginning with the tradition recorded by Eusebius of Caesarea that St. Mark was first preached the Gospel in Alexandria, where from Christianity spread throughout Egypt, we aim to achieve an overview of the key moments (until the early fourth century) of the spreading and evolution of Christianity along the Nile Valley. In this endeavour we present and analyse the list of bishops of Alexandria offered by Eusebius in the pages of his Church History, we emphasize the importance of the papirological sources in the process of evaluation the evolution of Egyptian Christianity, then we will make a stop to the persecution of Septimius Severus and a brief analysis of the episcopate of Dionysius. In the last part of the study we dwell on Meletian schism and persecution initiated by Diocletian, which ends with the death of St. Peter, considered the last of the martyrs.