The Anatolian beylik of Menteş (1260–1424), with capital in Milas in southwest Anatolia and headquartered in Beçin castle near that city, was one of the frontier principalities established by OghuzTurkish clans after the decline of the Seljuk Sultanate of Rum. The Beylik was named after its founder, Menteş Bey. It had come into existence by the year 1290. The beylik's core territory corresponded roughly to ancient Caria or the later Muğla Province in Turkey, including the province's three protruding peninsulas.
Among important centers of the Beylik were the cities of Beçin, Milas, Balat, Elmali, Finike, Kaş, Mağrı (Fethiye after 1911), Muğla, Çameli, Acıpayam, Tavas, Bozdoğan and Çine. The city of Aydın (formerly Tralles) was controlled by this Beylik for a time and was named Güzelhisar under the Menteşe. They later transferred it to their northern neighbors of Aydinids who renamed the city after the founder of their dynasty. Beys of Menteş also held Rhodes between 1300–1314 and were a serious regional naval power of their time. They also left important works of architecture such as the Firuz Bey Mosque in Milas and İlyas Bey Mosque in Balat.
Menteş Beys submitted to Ottoman power for the first time in 1390 under the reign of Bayezid I the Thunderbolt. After 1402, Tamerlane restored the beylik to Menteşoğlu İlyas Bey, who later recognized Ottoman sovereignty in 1414. It was incorporated into the Ottoman realm in a definite manner in 1426.
The present-day Muğla Province of Turkey was named the sub-province (sanjak) of Menteşe until the early years of the Republic of Turkey, although the province seat was moved from Milas to Muğla with the establishment of Ottoman rule in the 15th century.