Sisygambis was the mother of Darius III of Persia, whose reign was ended during the wars of Alexander the Great. After she was captured by Alexander at the Battle of Issus, she became devoted to him, and Alexander referred to her as "mother".
She may have been the daughter of king Artaxerxes II Memnon, or possibly of his brother Ostanes. If the latter, she married her own brother Arsames (an ancient Achaemenid tradition). She gave birth to Darius, Oxyathres, and possibly also Stateira I.
At the Battle of Issus (333 BC), Darius' army was routed and the Persian king fled the field, leaving his extended family, including his mother, his wife Stateira I, his children, and many others to the mercy of Alexander. Alexander captured them but treated them well. When Alexander the Great and Hephaestion went together to visit the captured Persian royal family, Sisygambis knelt to Hephaestion to plead for their lives, mistaking him for Alexander, because he was the taller, and both young men were wearing similar clothes. When she realized her mistake, she was acutely embarrassed, but Alexander reassured her with the words, "You were not mistaken, Mother; this man too is Alexander."