Ziaelas: king of of Bithynia (r. 254-228 BCE).
When Nicomedes I of Bithynia died in 255 BCE, he left sons from two marriages: from Ditizele, a lady from Hellespontine Phrygia, he had sons named Ziaelas and Prusias, and several other children from his second wife Etazeta. Nicomedes preferred the younger children as successors and passed over Ziaelas, who went into exile in Armenia, where he was received by a king who may be identified with Samus.note[Memnon of Heracles, fragment 14.]
Nicomedes had tried to prevent a civil war by appointing Ptolemy II Philadelphus of Egypt and Antigonus II Gonatas of Macedonia as guardians, together with the cities of Byzantium, Heraclea, and Cius, but it was in vain. When Etazeta became queen, Ziaelas hired Galatian mercenaries and conquered Bithynia. In the end, his stepmother found refuge in Macedonia.
The Galatians were not always reliable mercenaries: in 228, Ziaelas had to fight against his former allies and was killed in action. He was succeeded by his son Prusias I the Lame.