In Greek mythology, the Daughters of Danaus (/dəˈneɪɪdiːz/; Greek: Δαναΐδες), also Danaids, Danaides or Danaïdes, were the fifty daughters of Danaus. In the Metamorphoses, Ovid refers to them as the Belides after their grandfather Belus. They were to marry the fifty sons of Danaus's twin brother Aegyptus, a mythical king of Egypt. In the most common version of the myth, all but one of them killed their husbands on their wedding night, and are condemned to spend eternity carrying water in a sieve or perforated device. In the classical tradition, they came to represent the futility of a repetitive task that can never be completed (see also Sisyphus).
Danaus did not want his daughters to go ahead with the marriages and he fled with them in the first boat to Argos, which is located in Greece near the ancient city of Mycenae.
Danaus agreed to the marriage of his daughters only after Aegyptus came to Argos with his fifty sons in order to protect the local population, the Argives, from any battles. The daughters were ordered by their father to kill their husbands on the first night of their weddings and this they all did with the exception of one, Hypermnestra, who spared her husband Lynceus because he respected her desire to remain a virgin. Danaus was angered that his daughter refused to do as he ordered and took her to the Argives courts. Lynceus killed Danaus as revenge for the death of his brothers and he and Hypermnestra started the Danaid Dynasty of rulers in Argos.