Kios, with its present name Gemlik, is a very ancient and long standing residential area. Xenophon mentioned about the foundation of Kios with the mythological stories in Hellenica. Also the famous geographer Strobon writes that Kios was founded by one of the Argonouts. According to the myth, when the Argonouts stopped in the Golf of Gemlik , Hercules’/Heracles’ young friend Hylas goes to Kios river in order to take water and the nymphs kidnap him. Heracles stays there for a long time in order to find his friend and in time a city is established there. This myth can also be seen in the stories transferred by the Greek historian Apollodoros from the narratives of Polyphos.

During its history, Kios/Gemlik continued to be a residential area under the domain of Lydia, Persians, Ions, Alexandre The Great, Britons, Romans, The Byzantines and then stayed under the invasion of crusader armies and finally, under Ottoman sovereignty. It has always been an important harbour city and is also known as the center of olive cultivation and silk worm breeding.