The Danaids were the fifty daughters of Danaus, who ruled over Libya. Danaus’ brother Aegyptus, meanwhile, ruled over Egypt. When Aegyptus wished to arrange a marriage between his fifty sons and Danaus’ fifty daughters, Danaus and the Danaids fled to Argos, their ancestral homeland.
In Argos, Danaus and the Danaids were taken in by King Pelasgus (who in some traditions turned his throne over to Danaus). But the Argives failed to protect the Danaids from Aegyptus, who came to Greece with an army and forced his nieces to marry his sons.
In protest of this arrangement, the Danaids all killed their new husbands on their wedding night—all except Hypermnestra, who spared her husband Lynceus and subsequently became the ancestor of a line of Argive kings.
Various retellings of the story of the Danaids were known in antiquity, though only a few have survived (perhaps the most familiar being Aeschylus’ Suppliant Women). In many late traditions, the Danaids were viewed as treacherous murderers who were punished in the Underworld by being forced to forever draw water using leaking vessels.