Philip III Arrhidaeus (ca.

359 BCE – December 25, 317 BCE) is the king of Macedon from after June 11, 323 BCE until his death.

He is a son of King Philip II of Macedon by Philinna of Larissa, allegedly a Thessalian dancer, and a half-brother of Alexander the Great.

Named Arrhidaeus at birth, he assume the name Philip when he ascend to the throne.

As Arrhidaeus grew older it became apparent that he had mild learning difficulties.

In Plutarch's report, he became disabled by means of pharmaka (drugs/spells) attempt by Philip II's wife, Queen Olympias, who wanted to eliminate a possible rival to her son Alexander.

However, this claim is unlikely to be true.

Alexander was very fond of him, and took him on his campaigns, both to protect his life and to ensure he would not be used as a pawn in a challenge for the throne.

After Alexander's death in Babylon, Arrhidaeus was proclaimed king by the Macedonian army in Asia.

However, he was a mere figurehead, and a pawn of the powerful generals, one after the other.

His reign and his life did not last long.

The crater Ariadaeus on the Moon is named after him.