The island was colonised by Dorian Greeks, who named it Megiste. Inscriptions found at the foot of the Knight's castle confirm that during the Hellenistic period the island was ruled by Rhodes, and formed part of its Peraia. The Rhodians sent an overseer, or epistatis, to monitor events on the island.
During the period of the Byzantine Empire, Kastellorizo was part of the 'Eparchy of the Islands', the capital of which was Rhodes. In 1306 the island was taken over by the Knights of St. John Hospitaller of Jerusalem, headed by Folques de Villaret.
They were on their way from Cyprus to Rhodes, which was conquered three years later, becoming the centre of their Crusader State. They restored the castle, which was thereafter used as prison for disobedient knights. In 1440 the island was occupied by Sultan Djemal-el-din of Egypt, who destroyed the castle.
Ten years later it was conquered by Alfonso V of Aragon, king of Naples, who in 1461 rebuilt the castle and dispatched a governor. Naples retained possession of it until 1512, when it was conquered by Ottoman Sultan Suleiman I.
On 22 September 1659, during the war over Crete, the island was conquered by Venice and the castle was destroyed again, but the Ottomans were able to regain it again soon after. Between 1828 and 1833 Kastellórizo joined the Greek insurgents, but after the end of the Greek War of Independence it came back in possession of the Ottoman Empire.
In 1912, during the Libyan war between Italy and the Ottoman Empire, the inhabitants asked Giovanni Battista Ameglio (it), chief of the Italian occupation forces in Rhodes, for their island to be annexed to Italy. This was refused, and on 14 March 1913 the local population imprisoned the Turkish governor and his Ottoman garrison and proclaimed a provisional government.
In August of the same year, the Greek government sent from Samos a provisional governor supported by gendarmes. But they, too, were expelled by the inhabitants on 20 October 1915.
On 28 December 1915, the French navy led by the cruiser Jeanne d'Arc occupied the island at the behest of a pro-French local party which feared Turkish reprisals. The French quickly blocked another landing attempted on the same day by a Greek contingent of Evzones. Turkish shore batteries responded to the French occupation by shelling the island, in 1917 succeeding in sinking the British seaplane carrier HMS Ben-my-Chree.
In the Treaty of Sèvres the island was assigned to Italy and the Italian navy assumed it from the French on 1 March 1921, but the treaty was never ratified.
The Treaty of Lausanne confirmed the Italian claim on Kastellórizo, and the island - under the Italian name Castelrosso - was then integrated in the possession of the Isole Italiane dell'Egeo.
Edited by: Yallou