Achilles, properly Aehilleus, the hero of the Iliad, was the son of Peleus, king of the Myrmidons in Phthiotis in Thessaly, grandson of Aeacus, and thus third in descent from Zeus. His mother was the sea goddess Thetis, daughter of Nereus; hence he is often called Pelides, Pelei'ades, and .Aeacides. The story of his early life is told in different ways. One account is, that his mother, foreseeing his early death, endeavored to save him by dipping him in the river Styx, whose waters had the property of rendering the human frame invulnerable. The heel by which she held the babe was not wetted, and remained the sole vulnerable point of the hero. He was educated by Phoenix, who taught him war and eloquence, and by Chiron the centaur, who taught him the healing art. To keep him out of danger, Thetis disguised him as a maiden, and sent him to the court of Lycomedes, king of Scyros. Here his real character was soon discovered by the birth of a son to him, named Neoptolemus or Pyrrhus, by Deidamia, the daughter of Lycomedes. The prophecy was that Troy would never be taken in the absence of Achilles, and the crafty Ulysses was sent to discover him.

Disguised as a peddler, he offered the Scyrian maidens female trinkets and weapons of war; all of them chose ornaments, but the disguised hero clutched the sword and shield. He went to Troy, accompanied by his tutor Phoenix and his friend Patroclus, and at the head of his Myrmidons, in 50 ships of war. Previous to his dispute with Agamemnon he ravaged the country round Troy, and took and destroyed 12 towns on the coast and 11 in the interior. Brise'is was his favorite female slave and concubine, whom he had captured at the sack of Lyrnessus. The commander-in-chief, Agamemnon, claimed her as indemnity for his slave Chryseis. Achilles obeys on the entreaty of Minerva, but retires to his tent in wrath and resentment, refusing to take further part in the campaign. The Greeks suffer a myriad of woes in his absence, but no calamity will change his decision. At last his bosom friend Patroclus gains his permission to put on the armor of Achilles, and show himself to the Trojans. Believing that Achilles has come, they flee in panic.

Patroclus presses on, and is slain by Hector. Then Achilles, in the desire to avenge his friend, reconciles himself with Agamemnon, receives Briseis again, gets a new suit of armor from Vulcan, including the far-famed shield, which is brought to him by his mother, and rushes into the fight. He slaughters a great number of Trojans, contends with the river god Xanthus, whose course he has heaped with corpses and defiled with blood, and drives all the Trojans within the walls of their city. Hector alone dares to withstand his course. Achilles chases him three times around the walls of Troy, slays him, and, tying the body to his chariot, drags it into the camp of the Greeks. He institutes games in honor of his friend, and slays 12 captive Trojan youths on the funeral pyre, to satisfy the manes of Patro-clus. Priam, led by Mercury, penetrates to his tent, and prevails upon him to allow the body of Hector to be ransomed. We hear no more of Achilles in the Iliad. The accounts of his death are various. One represents him as falling by the arrow of Paris, directed by Apollo at the vulnerable heel, when he was in the temple of that god, about to espouse at the altar Polyxena, the daughter of Priam. His remains were collected in a golden urn, and a cenotaph was erected to him on the promontory of Sigeum. This monument was always an object of veneration to the Greeks; Alexander the Great performed a pilgrimage to it, and ran naked three times around it.