The play is set in Troezen, a coastal town in the northeastern Peloponnese. Theseus, the king of Athens, is serving a year's voluntary exile after having murdered a local king and his sons. His illegitimate son Hippolytus, whose mother is the Amazon Hippolyta, has been trained here since childhood by the king of Troezen, Pittheus.
At the opening of the play Aphrodite, Goddess of love, explains that Hippolytus has sworn chastity and refuses to revere her. Instead, he honors the Goddess of the hunt, Artemis. This has led her to initiate a plan of vengeance on Hippolytus. When Hippolytus went to Athens two years previously Aphrodite inspired Phaedra, Hippolytus' stepmother, to fall in love with him.
Hippolytus appears with his followers and shows reverence to a statue of Artemis, a chaste goddess. A servant warns him about his overt disdain for Aphrodite, but Hippolytus refuses to listen to him.
The chorus, consisting of young married women of Troezen, enters and describes how Theseus's wife, Phaedra has not eaten or slept in three days. Phaedra, sickly, appears with her nurse. After an agonizing discussion, Phaedra finally gives in to her nurse's demands and confesses why she is ill: she loves Hippolytus. The nurse and the chorus are shocked. Phaedra explains that she must starve herself and die with her honor intact. However, the nurse quickly retracts her initial response and tells Phaedra that she has a magical charm to cure her. However, in an aside she reveals different plans.
The nurse tells Hippolytus of Phaedra's desire and perhaps suggests that Hippolytus consummate her passion, after making him swear an oath that he will not tell anyone else. He reacts with a furious tirade on his hatred of women and threatens to tell Theseus everything when he arrives. Phaedra believes she is ruined. After making the chorus swear secrecy, she goes inside and hangs herself.
Theseus returns and discovers his wife's dead body. Because the chorus is sworn to secrecy, they cannot tell Theseus why she killed herself. Theseus discovers a letter on Phaedra's body, which asserts that she was raped by Hippolytus. Enraged, Theseus curses his son to death or at least exile. To execute the curse, Theseus calls upon his father, the god Poseidon, who has promised to grant his son three wishes. Hippolytus enters and protests his innocence but cannot tell the truth because of the binding oath that he swore. Taking his wife's letter as proof, Theseus exiles his son.
The chorus sings a lament for Hippolytus.
A messenger enters and describes a gruesome scene to Theseus; as Hippolytus got in his chariot to leave the kingdom, a bull roared out of the sea, frightening his horses, which dashed his chariot among the rocks, dragging Hippolytus behind. Hippolytus seems to be dying. The messenger protests Hippolytus' innocence, but Theseus refuses to believe him.
Theseus is pleased with Hippolytus' suffering until Artemis appears and tells him the truth. She explains that his son was innocent and that it was Phaedra who lied. Although the goddess admonishes Theseus' decision, she ultimately recognizes that the blame falls on Aphrodite. Hippolytus is carried in half alive, and Artemis promises to take revenge on Aphrodite by punishing the next person that Aphrodite loves. Finally, Hippolytus forgives his father, and then he dies.