The Maenads were not a fixed group of named individuals but a collective of women who answered the call of Dionysus, the son of Zeus and the mortal Semele, the Theban princess who had been burned to ash when she demanded to see Zeus in his true divine form. Dionysus was born from Zeus's thigh after Semele's death, and he grew up in the wild mountains of Nysa, raised by nymphs and taught the secrets of the vine. When he came of age, he travelled across the world spreading the cultivation of wine and the ecstatic worship that accompanied it, accompanied by a train of satyrs, the half-man half-goat spirits of the wilderness, and by bands of women who had fallen under his spell. These women were the Maenads, and they came from every class of Greek society: queens and princesses, housewives and slaves, young girls and grandmothers. Once they heard the call of the god, they left their looms and their children, cast off their veils and their shoes, and ran into the mountains, their hair unbound, their robes flying, their voices raised in the high-pitched cry called the ololuge.

The worship of the Maenads was not gentle. They carried the thyrsus, a staff topped with a pine cone and wrapped in ivy or vine leaves, a symbol of the god's power that could also be used as a weapon. They wore fawn-skins draped over their shoulders and wreaths of ivy or serpents in their hair. They danced in circles on the mountainside, whirling faster and faster until they entered a state of ecstatic possession, the enthousiasmos, in which the god himself was believed to dwell within them. In this state they performed miracles: fire did not burn them, weapons could not wound them, and water sprang from the earth at the strike of a thyrsus. But the most famous and most terrible of their rites was the sparagmos, the tearing apart of living animals. They would hunt down a bull, a goat, or a fawn, seize it with their bare hands, and rip it to pieces, distributing the raw flesh among themselves and eating it while it was still warm and bloody. They believed that in consuming the raw meat they were consuming the god, that Dionysus was present in the blood of the beast, and that by eating him they achieved a mystical union with the divine.

The most famous story of the Maenads is the destruction of Pentheus, the king of Thebes and the cousin of Dionysus, who refused to acknowledge the god's divinity. Pentheus was the son of Agave, the daughter of Cadmus, the Phoenician prince who had founded Thebes by sowing the teeth of a dragon into the earth, and of Echion, one of the Spartoi, the armed men who had sprung from those teeth. When Dionysus returned to Thebes and demanded that the city worship him, Pentheus banned the rites and imprisoned the god's followers, declaring that Dionysus was a fraud and that the Maenads were simply women behaving shamefully. Dionysus, in disguise, was captured and brought before Pentheus, but he escaped his chains with divine ease and then, in a moment of cruel irony, offered to show the king the secret rites of the Maenads, promising that Pentheus could spy upon them from the trees. Pentheus, driven by curiosity and contempt, agreed, and Dionysus dressed him in a woman's robes and led him to Mount Cithaeron, the mountain that towered above Thebes, where the Theban women had been driven mad by the god and were dancing in the forest.

From the treetops, Pentheus watched the Maenads, but they sensed his presence. Dionysus called out to them, and the women, in their divine frenzy, saw not their king but a wild animal, a lion or a bull. They surrounded the tree and pulled it down, and Pentheus fell among them. His own mother Agave was the first to seize him, and in her madness she did not recognise her son. She tore off his arm, and the other Maenads fell upon him, ripping his flesh with their hands and teeth, tearing his body into pieces while he screamed for mercy. Agave, still possessed, lifted his severed head upon her thyrsus and carried it down the mountain in triumph, believing she had killed a mountain lion. When she returned to Thebes and her father Cadmus asked where her son was, she held up the head and declared that she had hunted the beast herself, a great trophy for Thebes. Only when Cadmus removed the ivy wreath from her head did the madness lift, and Agave saw what she had done. The horror of the scene, the mother who had murdered her son at the command of a god she had denied, became one of the most powerful images in all Greek tragedy.

The Maenads were not only a Theban phenomenon. At Delphi, the sanctuary of Apollo on the slopes of Mount Parnassus, a special group of Maenads called the Thyiades performed rites for Dionysus every other winter, during the months when Apollo was believed to be absent and Dionysus ruled in his place. The Thyiades climbed the mountain in the dead of winter, dancing through the snow and performing the same ecstatic rites that the Theban women had performed on Cithaeron. Pausanias, the Greek traveller who wrote a guide to the ancient world in the second century CE, reported that the Thyiades were still active in his day, and that he had seen them dancing on the mountainside. The Maenads were also worshipped in Thrace, the wild region north of Greece where Dionysus was said to have been born, and in Macedonia, where the women were particularly devoted to the god's rites. In every place, the pattern was the same: the god arrived, the women went mad, and the boundaries between human and animal, civilisation and wilderness, life and death, dissolved in a frenzy of wine and blood.