Some historians view Diocletian (c. 245 – c. 316 C.E.) as the first Byzantine emperor; others Constantine the Great (c. 275 - 337 C.E.); and still others Justinian I (483 - 565 C.E.).
Mõned ajaloolased peavad Bütsantsi esimeseks keisriks Diocletianust (u 245 – u 316 m.a.j), teised Constantinus Suurt (u 275 – 337 m.a.j) ja kolmandad Justinianus I (483 – 565 m.a.j).