Achilles, in Greek mythology, was the most valiant Greek warrior in the Trojan War. Achilles was the son of Peleus, King of the Myrmidons, and Thetis, a sea-goddess. When the Fates prophesied that Achilles would die in the Trojan War, Thetis bathed her infant son in the river Styx to make him immortal. Only the heel by which she held him remained vulnerable.
While Achilles was growing up, the Greek armies were preparing for their assault on Troy. Knowing that her son was fated to die if he took part in the war, A'dhilles' mother dressed him in woman's clothing and sent him to Skyros to live among the maidens in the court of King Lycomedes. When a prophet warned the Greeks that they could not conquer Troy without the aid of Achilles, they sent Odysseus, the King of Ithaca, to find him. Disguised as a peddler, Odysseus went to Skyros bearing a shield and a spear among his goods, and Achilles betrayed his identity by seizing the weapons. Odysseus then persuaded him to join the Greek expedition to Troy.
Achilles' heroic deeds at Troy are related in Homer's Iliad. In the tenth year of the Trojan War, Achilles quarreled with Agamemnon, leader of the Greek army, over the captive girl Briseis. Angered and insulted, Achilles withdrew from the battle. His friend Patroclus took his place in the fighting and was killed by Hector, Troy's bravest warrior. Achilles returned to the battlefield the next day. He killed Hector and dragged his body three times around the walls of Troy.
Achilles was killed by the Trojan prince Paris, who shot a poisoned arrow into his vulnerable heel. According to one version of the myth the arrow's flight was guided by the god Apollo.
The term "Achilles' heel" has become proverbial for referring to a weakness.