9. Son of Pyrrhus, king of Epeirus, by his wife Antigone, the step-daughter of Ptolemy Lagi. When only fifteen years of age he was left by his father in charge of his hereditary dominions, when Pyrrhus himself set out on his expedition to Italy, B. C. 280. (Just. 18.1.) Of his proceedings during his father's absence we know nothing : but immediately after the return of Pyrrhus, B. C. 274, we find Ptolemy actively co-operating with him, reducing Corcyra with a small force : and after the defeat of Antigonus Gonatas, repulsing him in an attempt to recover his lost kingdom, and inflicting on him a second defeat. He afterwards accompanied Pyrrhus on his expedition to the Peloponnese, B. C. 272, and took a prominent part in the attack on Sparta, but in the march from thence towards Argos, Areus having occupied the mountain passes, a severe combat ensued, in which Ptolemy, who commanded the advanced guard of his father's army, was slain. Young as he was, he had given the most striking proofs of daring courage and personal prowess, and, had his life been spared, would probably have rivalled the renown of his father. (Just. 25.3, 4; Plut. Pyrrh. 28, 30.)