Irene was born to a noble Greek family of Athens, the Sarantapechos family. Although she was an orphan, her uncle, Constantine Sarantapechos, was a patrician and possibly strategos of the theme of Hellas. She was brought to Constantinople by Emperor Constantine V on November 1, 769, and was married to his son Leo IV on December 17. Although she appears to have come from a noble family, there is no clear reason as to why she would have been chosen as Leo's bride, leading some scholars to speculate that she was selected in a bride-show, in which eligible women were paraded before the bridegroom, until one was finally selected.