The last king of Pergamum died in 133 BCE without an heir and bequeathed his kingdom to Rome. In 129 BCE the Roman republic claimed Anatolia as its own, establishing the province of Asia, with its capital at Ephesus. Roman rule brought increased commerce and prosperity to Anatoliaand provided fertile ground for the spread of a new religion. They built upon sites with good foundations left by the Lycians.  After the sack of Rome in 410 AD by Visigoths, the empire lived on in Constantinople and the East. Historians usually call this later Roman empire the Byzantine Empire.  Many of the Lycian sites have been built upon by the Romans, for example, Tlos and Patara. 

When the Roman emperor Constantine the Great moved the capital of the Empire from Rome to Byzantium and renamed it Constantinople, in 330 AD, that the Byzantine Empire really began. It lasted over 1000 years, ending finally in 1453 when the Ottoman Turks conquered Constantinople and renamed it Istanbul. 

Fethiye BCE was known as Telemessos. Fethiye was a very prominent city dedicated to the god Apollo and was the centre of prophecy. Ancient ruins include rock tombs, Lycian-type sarcophagi, a Roman theatre and a medieval castle.  The ancient castle stands at the place where the city was first founded. Its existing walls date back from the eleventh century. Rebuilt during the fifteenth century by the Knights of Rhodes, the castle was used as a naval base.  

In the Ottoman era, Mugla Province was known as Mentes with capital in Milas in southwest Anatolia and headquartered in Beçin castle near that city. Among important centres of the Beylik were the cities of Beçin, Milas, Balat, Elmali, Finike, Kas, Magrı (Fethiye after 1914), Mugla, Çameli, Acıpayam, Tavas, Bozdogan and Çine.

In 1914 the council of the municipality changed the name of Megri to Fethiye in honour of Fethi Bey, the first Turkish air force pilot who had crashed and died.