In Greek mythology, Thyraeus (Ancient Greek: Θυραίου or Θυραῖόν means 'at the door') was an Arcadian prince as one of the 50 sons of the impious King Lycaon either by the naiad Cyllene, Nonacris or by unknown woman. He was the reputed eponymous founder of the Arcadian city of Thyraeum. The Arcadians believed that both the Thyrea in Argolis and also the Thyrean gulf were named after Thyraeus.