Iasos or Iassos, also in Latinized form Iasus or Iassus, was a Greek city in ancient Caria located on the Gulf of Iasos, opposite the modern town of Güllük, Turkey. It was originally on an island, but is now connected to the mainland. It is located in the Milas district of Muğla Province, Turkey, near the Alevi village of Kıyıkışlacık, about 31 km from the center of Milas.