The daughter of Electryon and Anaxo and granddaughter of Perseus. She was married to her cousin and uncle Amphitryon, king of Thebes.
Alcmena was seduced by Zeus, who had taken the shape of her husband, and who would never again sleep with a mortal woman. She gave birth to two sons, Iphicles and Heracles, and when her husband was told by Tiresias that Zeus was the father of the latter, he never again slept with his wife for fear of the god's jealousy.
Hera was of course insane with jealousy of her husband's infidelity, and as a punishment she prolonged

Alcmena's labor, and also sent snakes to the children, which were killed by the already strong baby Heracles.
When her husband had died, Alcmena joined Heracles. He and his brother were just about to try to conquer Tiryns, but they failed and wen from there. Alcmena, however, stayed, and looked after some of her grandchildren. She was still there when Heracles died.
After her famous son's death she was forced to flee from Tiryns with her grandchildren, and so ended up in Athens. There Theseus son Demophon ruled, and he protected the woman. The king of Tiryns demanded that Demophon expel Alcmena, but the Athenian king refused and war broke out. This resulted in the death of the king of Tiryns, and when Demophon brought his head to Alcmena, she gouged out his eyes with her hairpins.
Alcmena died in Thebes when she was very old. Zeus, who had no forgotten her, replaced her body with a stone, and took her to the Island of the Blessed. There, she was young again, and married to Rhadamanthus.
When Heracle's children, the Heraclids, discovered that Alcmena's body had been replaced by a stone in the coffin they took it to Thebes where Alcmena was worshipped. She was also worshipped in Athens.