In Greek mythology, Pierus (Ancient Greek: Πίερος), was the king of Emathia in Macedonia. He was the eponym of Pieria and Mt. Pierus. Pierus was credited to be the first to wrote in the praise of the Muses.
According to Marsyas of Pella (c. 330 BC), Pierus was the son of Makednos by a local woman and brother of Amathus (Emathus), eponym of Emathia but Solinus (9.10) contradicts this idea because according to him Pierus was unrelated and older than Makednos.
In the Suda, he was described as a son of Linus, the son of Thracian Aethusa and in turn Pierus was the father of Oeagrus making him the grandfather of the musician Orpheus. While in the account of Antoninus Liberalis, Pierus sprung from the soil (an ).
Most of the myths recounted Pierus to have fathered the Pierides by Antiope, nymph of Pieria or Euippe of Paionia. An unnamed daughter of Pierus was said to be the mother of Orpheus, not the Muse Calliope as what the Greeks believed according to Pausanias.
(mother of Orpheus)
Pierus was famous for his daughters, the Emathides, nine maidens whom he named after the nine Muses. These girls, believing that their skills were a great match to the Muses, afterwards entered into a contest with the Muses. Being conquered, they were transformed into birds called Colymbas, Iyngx, Cenchris, Cissa, Chloris, Acalanthis, Nessa, Pipo, and Dracontis.