Wikipedia:

In Greek mythology, Phaedra /ˈfiːdrə, ˈfɛdrə/ (Ancient Greek: Φαίδρα, Phaidra) is the daughter of Minos and Pasiphaë, wife of Theseus, sister of Ariadne, and the mother of Demophon of Athens and Acamas. Phaedra's name derives from the Greek word φαιδρός (phaidros), which meant "bright".

Though married to Theseus, Phaedra fell in love with Hippolytus, Theseus's son born by either Hippolyta, queen of the Amazons, or Antiope, her sister. Euripides placed this story twice on the Athenian stage, of which one version survives. According to some sources, Hippolytus had spurned Aphrodite to remain a steadfast and virginal devotee of Artemis, and Aphrodite made Phaedra fall in love with him as a punishment. He rejected her.

In one version, Phaedra's nurse told Hippolytus of her love, and he swore he would not reveal her as a source of information. In revenge, Phaedra wrote Theseus a letter that claimed Hippolytus raped her. Theseus believed her and cursed Hippolytus with one of the three curses he had received from Poseidon. As a result, Hippolytus's horses were frightened by a sea monster and dragged their rider to his death.

Alternatively, after Phaedra told Theseus that Hippolytus had raped her, Theseus killed his son and Phaedra committed suicide out of guilt for she had not intended Hippolytus to die. Artemis later told Theseus the truth. In a third version, Phaedra simply told Theseus this and did not kill herself; Dionysus sent a wild bull which terrified Hippolytus's horses.