Dionisi wa Aleksandria, aliyeitwa Mkuu, alikuwa Patriarki wa 14 wa mji huo wa Misri tangu tarehe 28 Desemba 248 hadi kifo chake tarehe 22 Machi 264. Mwaka 252 tauni ilipozuka mjini, yeye na mapadri wake walijitosa kuwahudumia walioambukizwa. Baadaye alipelekwa uhamishoni wakati wa dhuluma ya kaisari Valerian. Tangu kale anaheshimiwa na Wakatoliki, Waorthodoksi na Waorthodoksi wa Mashariki kama mtakatifu. Sikukuu yake huadhimishwa tarehe 8 Aprili. Watakatifu wa Agano la Kale Orodha ya Watakatifu Wakristo Orodha ya Watakatifu wa Afrika Orodha ya Watakatifu Wafransisko Mababu wa Kanisa Called "the Great" by Eusebius, St. Basil, and others, he was characterized by the Catholic Encyclopedia as "undoubtedly, after St. Cyprian, the most eminent bishop of the third century... like St. Cyprian, less a great theologian than a great administrator." Eusebius of Caesarea, the author of Ecclesiastical History in the 4th century, states that Saint Mark came to Egypt in the first or third year of the reign of Emperor Claudius, i.e. 41 or 43 A.D. "Two Thousand years of Coptic Christianity" Otto F. A. Meinardus p28.