In greek mythology, Dia was described as a queen of the Lapith tribe in Thessalia, and wife of king Ixion. Dia was the daughter of Delioneus (or Eioneus). When Ixion married Dia, he did not pay the bride price, the tradition gift grooms gave to their father-in-law. Dia's father was rightly offended at this and in retaliation stole a few of Ixion's horses. In response, Ixion invited his father-in-law to a feast, where Ixion pushed him into a pit filled with burning coals and wood. Ixion was first man guilt of kin-staying in Greek mythology. By Ixion, Dia became the mother of Pirithous and Phisadie.
According to other version, by Zeus, Dia became the mother of Pirithous. Zeus disguised as a horse, have sex with her. Pirithous which means "to run around". Dia's son Pirithous, who received his name from the circumstance, that Zeus when attemp to seduce Dia, ran around her, in the form of a horse.
In Greek mythology, Dia is also used as a surname of Hebe or Ganymede, who had temple under this name at Phlius and Sicyon.