Ptolemy Keraunos

Ptolemy Keraunos (Greek: Πτολεμαῖος Κεραυνός, died 279 BC) was the King of Macedon from 281 BC to 279 BC. His epithet Keraunos is Greek for "Thunder" or "Thunderbolt".

He was the eldest son of Ptolemy I Soter, ruler of Egypt, and his third wife Eurydice, daughter of the regent Antipater. His younger half-brother, also called Ptolemy, became heir apparent and, in 282 BC, ascended to the throne as Ptolemy II. Ptolemy Keraunos had left Egypt and arrived at the court of Lysimachus, the king of Thrace, Macedon, and part of Asia Minor. His half-sister, Arsinoe, later to be named Arsinoe II of Egypt, was wife of Lysimachus.

While staying in the court of Lysimachus, Arsinoe's intrigues led to the accusation of Lysimachus' first son, Agathocles, of treason and to his execution. Keraunos sided with his other sister (from the same mother) Lysandra, who was Agathocles' wife, and accompanied her to the court of Seleucus in the East to solicit his aid. Seeing an opportunity to intervene for his own gain in the politics of both Lysimachan Thrace and Ptolemaic Egypt, Seleucus prepared an expedition against Lysimachus shortly afterwards.