Irene of Athens (Greek: Εἰρήνη, Eirénē; c. 752 – 9 August 803), surname Sarantapechaina (Σαρανταπήχαινα), was Byzantine empress consort to Emperor Leo IV from 775 to 780, regent during the childhood of their son Constantine VI from 780 until 790, co-ruler from 792 until 797, and finally empress regnant and sole ruler of the Eastern Roman Empire from 797 to 802. A member of the politically prominent Sarantapechos family, she was selected as Leo IV's bride for unknown reasons in 768. Even though her husband was an iconoclast, she harbored iconophile sympathies. During her rule as regent, she called the Second Council of Nicaea in 787, which condemned iconoclasm as heretical and brought an end to the first iconoclast period (730–787).

She was influential in government policies during her husband's reign. His untimely death caused the throne to actually fall to her, who was solely in charge. As Irene's son Constantine reached maturity, he began to move out from under the influence of his mother. In the early 790s, several revolts tried to proclaim him as sole ruler. One of these revolts succeeded, but in 792, Irene was re-established in all imperial powers as co-emperor with Constantine. In 797, Irene organized a conspiracy in which her supporters gouged out her son's eyes, maiming him severely. He was imprisoned and probably died shortly afterwards. With him out of the way, Irene proclaimed herself sole ruler. Pope Leo III—already seeking to break links with the Byzantine East—used Irene's alleged unprecedented status as a female ruler of the Roman Empire to proclaim Charlemagne emperor of the Holy Roman Empire on Christmas Day of 800 under the pretext that a woman could not rule and so the throne of the Roman Empire was actually vacant. A revolt in 802 overthrew Irene and exiled her to the island of Lesbos, supplanting her on the throne with Nikephoros I. Irene died in exile less than a year later.