She was the daughter of Cyrus the Great and the sister of Cambyses II. Cambyses insisted on marrying her, although there was no legal precedent for this in Persia; to avoid offending the king, Cambyses' advisors instead informed him that the laws allowed him to do whatever he wished. Atossa then married Smerdis, who overthrew Cambyses, and in 522 BC she married Darius I when Darius overthrew Smerdis. Xerxes I was one of their children.
Atossa probably died before Xerxes came to power, although Herodotus believed she was still alive during Xerxes' reign. Aeschylus also included her as a central character in his tragedy The Persians. Very little is known about the real Atossa, although it is speculated that she came from a Zoroastrian family, as Atossa is a mythical figure in that religion. According to Herodotus she also had Greek slaves, whom she preferred to Persian slaves.