Pierus (Greek: Πίερος), in Greek mythology, is a name attributed to two individuals:
Pierus, the eponym of Pieria, son of Makednos and father by Antiope or Euippe of the of Pierides, nine maidens who wanted to outshine the Muses. They afterwards entered into a contest with the Muses, and being conquered, they were transformed into birds called Colymbas, lyngx, Cenchris, Cissa, Chloris, Acalanthis, Nessa, Pipo, and Dracontis. These names were taken from actual names of birds in ancient Greek, such as the wryneck, hawk, jay, duck, goldfinch, and four others with no recognizable modern equivalents. Pierus is sometimes said to be have been father of Linus or Oeagrus and therefore the grandfather of Orpheus.
Pierus, son of Thessalian Magnes and Meliboea, was the lover of muse Clio and father of Hyacinth and Rhagus. Pierus was loved by muse Clio because Aphrodite had inspired her with the passion, as a punishment for deriding the goddess' own love for Adonis.
According to Solinus (9.10), Pierus was unrelated and older than Makednos.
See also: Pieres a Thracian tribe
References: Pierre Grimal The Dictionary of Classical Mythology