Perinthus or Perinthos (Ancient Greek: ἡ Πέρινθος) was a great and flourishing town of ancient Thrace, situated on the Propontis. According to John Tzetzes, it bore at an early period the name of Mygdonia (Μυγδονία). It lay 35 kilometres (22 mi) west of Selymbria and 90 kilometres (56 mi) west of Byzantium, on a small peninsula of the bay which bears its name, and was built like an amphitheatre, on the declivity of a hill. Its site is near modern Marmara Ereğlisi, in Turkey.