What was the only vulnerable spot on Achilles' body?

The only vulnerable spot on Achilles' body was his heel. In the best-known later version of the myth, Achilles's mother, Thetis, tried to make him invulnerable by dipping him in the River Styx. She held him by one heel, leaving that small area untouched by the river's protection.

During the Trojan War, Achilles became Greece's greatest warrior, but the unprotected heel remained a fatal weakness. Paris, prince of Troy, eventually shot Achilles with an arrow; later traditions variously say the arrow was guided by Apollo or poisoned. The wound killed him despite his otherwise extraordinary strength.

The detail is often called the “Achilles' heel,” meaning a hidden weakness in someone or something powerful. A common mix-up is assuming the scene appears in Homer's Iliad: the epic ends before Achilles's death, and versions differ about whether the wound struck the heel, ankle, or another part of the body.