The daughter of Cadmus and Harmonia. Her sisters were Autonoe, Ino and Semele, and she also had a brother: Polydoros. She was married to Echion, who was one of the Sparti who had been born out of the dragon's teeth that Cadmus had sown when founding Thebes. Together with Echion she had a son: Pentheus.
When Semele was killed after she had gotten pregnant with Zeus Agave and her sisters spread the rumour that their sister had been promiscuous. They said that Semele had been so ashamed of being pregnant that she said that she had slept with a god. Therefore, the sisters said, she got what she deserved.
Semele's child, Dionysus, had been saved, and Agave and her sisters were to become his followers. Pentheus, who was curious to see what his sisters were up to in the forests, hid in a tree one day and spied on them. When they discovered him they tore him to pieces, but were forced to worship the tree afterwards.
Agave was later to go with her father to Illyria where she married the king Lycotherses. She later killed hi so that her father could take the throne.