Irene was born to the noble Greek Sarantapechos family of Athens.

Although she was an orphan, her uncle Constantine Sarantapechos is a patrician and possibly strategos of the theme of Hellas.

She is brought to Constantinople by Emperor Constantine V on November 1, 769 and is married to his son Leo IV (crowned co-emperor by his father in 751), on December 17.

Although she appears to have come from a noble family, there is no clear reason 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.

Leo IV had in 768 married an Athenian-born sixteen-year-old named Irene, who two years later had presented him with a son.

At the request of the army and with the support of the Senate and the citizens, Leo now crowns him coemperor as Constantine VI, passing over the caesar Nicephorus, a stepbrother of Leo.

The resulting conspiracy in favor of Nicephorus is suppressed, and the conspirators exiled.

Leo profits from discord among the Bulgarians by granting the Bulgarian khan Telerig asylum in Constantinople from 776 to 777 and marrying him to a cousin of his wife Irene.

He also conducts three campaigns against the Arabs in Anatolia and Syria from 777.

Telerig, despite his apparent success, finds it necessary to flee Bulgaria to Leo IV the Khazar in 777.

The imperial government grants Telerig asylum and the title of patrikios.

Telerig converts to Christianity under the name of Theophylaktos and marries a cousin of the Empress Irene.

The Muslims escalate their annual raids against the Empire by invading Anatolia in force in 778, but imperial troops repulse the invasion at the Battle of Germanicopolis, killing thousands of Muslims during and after the battle.

Leo at the beginning of his reign had not attempted to continue the fierce iconoclastic policy pursued by his father and grandfather, forbidding the use of icons.

Instead, he has shown considerable moderation toward the proponents of icons, even appointing them to bishoprics.

This action may have resulted from the influence of the strongly orthodox Irene.

In 780, however, he reverses his policy and initiates a persecution of those favoring the use of icons.

He dies prematurely, at thirty-one, on September 8, 780, leaving to succeed him his nine-year-old son, Constantine VI, under the regency of the empress Irene.

Later in this year, Irene crushes what seems to have been a plot by the Iconoclasts to put Leo's half brother, Nikephoros, on the throne.

Caliph al-Mahdi, in retaliation for the Romans' post-battle slaughter of his army in 778, has assembled a large force of Mesopotamians, Syrians, and Khorasanians, which he leads northwards in late 780 Aafter the death of Emperor Leo IV, who had campaigned against the Arabs in Anatolia and Syria since 777.

Empress Irene, acting regent for her young son Constantine VI, orders the imperial forces to annihilate the invading Muslims.

Leo's widow Irene becomes guardian of their ten-year-old son, Constantine VI, and co-emperor with him.

Irene decries the practice of forced conversion, and, with clerical support, calls for conversion only of those who voluntarily confess and rejects Judaism and its “customs and pursuits.”

The Romans had initiated another war with the Bulgarians in 780, pushing the Bulgarian frontier to the north by 783, when hostilities cease.

The caliph's teenaged son, Harun al-Rashid, has led a number of charges against the Romans, his several victories enabling the Muslims' westward advance.

Reaching the Bosporus in 783, the Muslims defeat the Romans at Nicomedia (Izmit of Kocaeli).

Trapped on his return march, he is rescued by the defection of the imperial general Tatzates, with many of his men.

His defection, however, is kept secret for a while, allowing Harun to seize the imperial envoys, Staurakios among them, who had come to negotiate a truce.

The Abbasid commander was thus able to dictate harsh terms to Empress-regent Irene of Athens, who promises tribute.

Harun appoints Tatzates as governor of Armenia.