Ancient city of Tium, also known as Tios or Filyos, is an ancient city located on the south coast of the Black Sea in Zonguldak Province in northern Turkey. It was founded as a colony of the Greek city of Miletus in the 7th century BC. In subsequent periods, the city became part of the Hellenistic Kingdom of Bithynia, and then became a Roman province in 74 BC. The city continued to flourish during the Roman and Byzantine eras, and then gradually diminished in importance with time. Among the most important remaining monuments in the city are the port and the Roman theater, in addition to the Byzantine church.