The island's first inhabitants were the Pelasgians. In 480 B.C., when the Persians invaded Greece, Skiathos  island tried to defend itself with three ships against the Persian fleet. After the Persian wars, it joined the First Athenian Alliance. Later, it succumbed to the Macedonians and was subsequently attacked by Attalus, the Rhodians, the Romans, Philip III and Demetrios Poliorcetes. Eventually, it became a hideout for pirates and was awarded autonomy by Septimius Severus (193-211 A.D.). Under the Frankish occupation it was a part of the Ghizi's duchy before being taken over by the Venetians (1454) who fortified the Bourtzi islet and the castle. In 1538-1829 the inhabitants removed to an almost inaccessible position on the most northerly tip of the island. The Kastro, as the deserted town is called, is a three hours distance from Skiathos  island Town. It is built on a rocky peninsula connected to the rest of the island by a drawbridge. Of its ruined buildings, the Church of Christ is the best preserved, with a wooden screen of 1695 and some of its frescoes more or less intact. Once of great importance but now inhabited by only one or two monks, are the Monastery of Evangelistria and the Convent of St. Charalambos.
In 1538, Skiathos  island was ransacked by the Turkish soldiers under Haireddin Barbarossa and the population suffered terribly. Later it became a refuge for revolutionaries from Pelion and Macedonia. After 1829, its people abandoned their fortress capital on the northern side of the island and built the present town, known as Chora. Skiathos  island gave birth to two famous writers, Alexandros Papadiamantis (1851-1911) and Alexandros Moraitidis (1851-1929).
During the Greek War of Independence of 1821 many warriors from Thessaly opposite took refuge on the island. During this war the ships of Skiathos  island played their part and the island was liberated in 1823.