The decline and fall of the Roman empire gave a fresh impetus to the pirates and to other would-be conquerors, who all renewed their attacks on Zakynthos. For decades, Barbary corsairs, Goths, Vandals, Huns and other hordes scourged Zakynthos and the other Eptanissos islands of the Ionian and the western Mediterranean generally. They plundered, murdered and destroyed ruthlessly, the stubborn resistance of the local inhabitants notwithstanding. Wave after wave of raiders overran the islands, stripped them bare, and left, only to return in due course in ever greater strength.
When Constantine the Great (c. 274-337 AD) founded the Byzantine empire, Zakynthos became part of the province of Illyria, governed by a reserve officer who had been assigned full powers.
Although under the protection of Constantinople, Constantine's name for his new seat of government, formerly known as the city of Byzantium, the island had somewhat less to suffer from the destructive raids of the pirates. After Constantine's death his squabbling successors neglected the outlying parts of the empire, and the raids and the pludering resumed in full force.
In terms of social organisation in the Byzantine era, the people of Zakynthos belonged to one of three classes. In the top class were the epiphaneis (upper crust), the big landowners of the island, the second class was comprised of artisans and merchants, and the third class consisted of farmers, who were further subdivided into those who owned their land, into leaseholders, and serfs.
Christianity came to Zakynthos early. There is a local tradition that in 34 AD Mary Magdalene came to the island en route from Jerusalem to Rome, and her ship anchored for a while on the western coast of Zakynthos where she preached the teachings of Jesus of Nazareth. There is still a village in that part of the island called Maries, where the memorv is celebrated every year with a special festival.
Zakynthos suffered extensive destruction in 466, when the African Vandal king Gizarich arrived with sixty ships and his men fell to plunder, rape and slaughter, and set fire to Zakynthos town. When Gizerich left, he took with him 500 of the 'upper crust' landowners, whom he butchered as his ships sailed out into the Adriatic and flung their bodies overboard.
The years that followed brought new pirate raids, by the Saracens this time, and new catastrophes. In 844 Byzantium sent out its commander Nikitas, and later on his deputy Nassar, who between them freed the island from the raiders who received harsh punishment. Around this time Zakynthos and Kephalonia were taken out of the province of Achaia and placed in the llth district of Longovarda. Later still, a specifically Byzantine district of Kefhalonia was formed, which included all the seven Ionian isles.