Casystes or Kasystes (Ancient Greek: Κασύστης) was a port town of ancient Ionia, near Erythrae. Strabo, whose description proceeds from south to north, after describing Teos, says, "before you come to Erythrae, first is Erae, a small city of the Teians, then Corycus, a lofty mountain, and a harbour under it, Casystes; and another harbour called Erythras."[1] It is probably the Cyssus of Livy,[2] the port to which the fleet of Antiochus III sailed (191 BCE) before the naval engagement in which the king was defeated by Eumenes II and the Romans.