Irene of Athens, surname Sarantapechaena, 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). Her public figure was very polarizing during her 5 year reign, as most saw it as wrong for a woman to rule solely. Her reign as such made her the first ever empress regnant, ruling in her own right, in Roman and Byzantine imperial history.
Solidus of Irene issued during her sole reign
Gold solidus showing Irene as regent along her son Constantine VI; Irene took control of the throne and ruled the empire solo until 790.
Irene of Athens (or Irene Doukaina) in the Pala d'Oro, Venice.
15th century mural depicting Irene and Constantine VI at the Seventh ecumenical council of 787.
Leo IV the Khazar was Byzantine emperor from 775 to 780 AD. He was born to Emperor Constantine V and Empress Tzitzak in 750. He was elevated to co-emperor in the next year, in 751, and married to Irene of Athens in 768. When Constantine V died in September 775, while campaigning against the Bulgarians, Leo IV became senior emperor. In 778 Leo raided Abbasid Syria, decisively defeating the Abbasid army outside of Germanicia. Leo died on 8 September 780, of tuberculosis. He was succeeded by his underage son Constantine VI, with Irene serving as regent.
Solidus of Leo IV and his son Constantine VI