Irene, empress of the Byzantine Empire 780-802 and sole ruler, 797-802.
Not many women ruled the Roman empire, but Irene ruled in her own name, 797-802. In the middle Byzantine centuries the wives of young male heirs were selected by assembling a number of the most beautiful young women in the empire and having them choose. It is not a surprise that an outstandingly beautiful young woman who was also intelligent and clever might outshine her husband.
During the reign of Constantine V (741-775) his son Leo IV (775-780) married Irene. When Leo died their son, Constantine VI, was only ten. She took the role of regent. His most common type actually features Irene on the obverse, with Constantine VI smaller on the reverse.
Irene facing, wearing loros and crown with triangular points--the crown of a female, and holding globus cruciger in her right hand.
Bust of Constantine VI holding globus cruciger in his right hand, above horizontal line. Below the line is a large M (the old symbol for a 40-nummis follis) with X to left and N to right, and A in the bottom of the M.
There are gold coins of Irene with an obverse like this and a facing bust of Constantine VI on the reverse, and later, during her sole reign, there are gold coins with her facing bust on both sides! The two sides are almost identical.
During her sole reign she did not issue silver. The next coin, a miliaresion, is the the only type of silver coin during their joint reign.
Constantine VI and Irene, struck between 780 and 797.
21 mm. 2.14 grams. Silver miliaresion.
IhSUS XPISTVS ҺICA (Jesus Christ conquers)
Constantine and Irene, by the grace of God, kings.
DOC III.I Constantine VI 4b.
During their joint reign it became clear that Constantine VI supported the iconoclasts (who destroyed icons and had been in power since Leo III in 717) and Irene was an iconodule. The army was mostly iconoclasts and much of the populace of Constantinople was iconodules, so each had numerous important supporters. With typical Byzantine ups and downs, including a year-long spell in exile, she managed to endure until she saw, in 797, that Constantine VI was unpopular enough that she could overthrow him. She had him brutally blinded (supposedly more humane than outright execution) and she took sole power.
She ruled alone from 797 to 802. The story has many interesting twists and turns, not least of which involved a potential marriage to Charlemagne, King of the Franks who had, in 800, been crowned by the pope "The Holy Roman Emperor."
Of course, in those days a woman, no matter how competent, was considered unsuitable as emperor. If she married Charlemagne the empire would be unified under a boorish westerner--unthinkable. She had to go. A palace revolution resulted in Nicephorus I (802-811) becoming the next emperor.
Byzantine history sure is, well, Byzantine!
Go to the page on "Emperors on Byzantine coins."