Hyrieus was a demigod and son a son of Poseidon.
Hyrieus was the son of Alcyone and Poseidon. He was also the brother of Hyperenor and Aethusa. By the nymph Clonia, he became the father of Nycteus and Lycus.
Hyrieus was the eponym of Hyria in Boeotia, where he dwelt and where Orion (see below) was born; some sources though place him either in Thrace or on Chios. He was said to have expelled Euonymus from the temple of Apollo.
Hyrieus hired Trophonius and Agamedes to build a treasure chamber for him but they also built a secret entrance to it, so that the treasury was easily accessible by removing just one stone from the outside. Using the secret entrance, they would come and steal some of Hyrieus' possessions. He was dumbfounded at discovering that his fortune was diminishing while the locks and seals remained intact; to catch the thief, he laid a snare. Agamedes was trapped in it; Trophonius cut off his brother's head so that Hyrieus would never know the thief's identity, and himself disappeared in a chasm of the earth. He became the adoptive father of Orion, the great hunter.