Tiresias was a Greek/Roman prophet who came from Thebes. He figures into several stories from Greek and Roman mythology.

One of the more amusing ones occured when he was walking down the road one day, and he saw two snakes having sex. For one reason or another, he took his walking stick and thrashed them badly. The Gods happened to notice this, and, as punishment, turned him into a woman. So he went around as a woman for a while. Seven years later, he saw two snakes lying side by side, and this time he used his walking stick to make them come together. This caused him to be turned back into a man. Later on, Zeus and Hera were having an argument about who has a better orgasm during sex. Remembering that Tiresias had been both a man and a woman, they decided to ask him. Tiresias replied that a woman's orgasm is nine times better.

The loser of the argument between Zeus and Hera struck Tresias with a lightning bolt, which blinded him. As compensation, the winning party gave him the ability to foresee the future.

Tiresias is seen again later on in the story of Odysseus/Ulysses, where he acts as a seer.