Macedonia, Philip III 323-317 BC Babylon, Tetradrachm, 16.80g

Philip III Arrhidaeus (Ancient Greek: Φίλιππος Ἀρριδαῖος, romanized: Phílippos Arrhidaîos; c. 357 BC – 317 BC) was king of the ancient Greek kingdom of Macedonia from 323 until his execution in 317 BC. He was a son of King Philip II of Macedon by Philinna of Larissa, and thus an elder half-brother of Alexander the Great. Named Arrhidaeus at birth, he assumed the name Philip when he ascended to the throne.

As Arrhidaeus grew older it became apparent that he had mild learning difficulties. Plutarch was of the view that he became disabled by means of an attempt on his life by Philip II's wife, Queen Olympias, who wanted to eliminate a possible rival to her son, Alexander, through the employment of pharmaka (drugs/spells); however, most modern authorities doubt the truth of this claim.^[1]

Alexander was fond of Arrhidaeus and took him on his campaigns^{[citation needed]}, both to protect his life and to prevent his use as a pawn in any prospective challenge for the throne. After Alexander's death in Babylon in 323 BC, the Macedonian army in Asia proclaimed Arrhidaeus as king;^[2] however, he served merely as a figurehead and as the pawn of a series of powerful generals.^[3]