Aegyptos was the son of King Belus[2] of Egypt and Achiroe, a naiad daughter of Nile,[3] or of Sida,[4] eponym of Sidon.
A scholium on a line in Euripides, Hecuba 886, reverses these origins, placing the twin brothers at first in Argolis, whence Aegyptus was expelled and fled to the land that was named after him.
When Aegyptus and his sons arrived to take the Danaïdes, Danaus relinquished them, to spare the Argives the pain of a battle; however, he instructed his daughters to kill their husbands on their wedding night.
Forty-nine followed through, but one, Hypermnestra ("greatly wooed"), refused, because her husband, Lynceus the "lynx-man", honored her wish to remain a virgin.
The story of Danaus and his daughters, and the reason for their flight from marriage, provided the theme of Aeschylus' The Suppliants.