Constance (Constantia, Constantina or Constantiana) was the eldest daughter of the Roman emperor Constantine the Great and his second wife Fausta. The date of her birth is unknown and the legend that developed in the Middle Ages around her veneration as a saint seems to have been a wild fabrication. The facts that are known about her life reveal her to be a complex and troubling character.
She married her cousin Hannibalianus, the King of Kings and Ruler of the Pontic Tribes, in 335 CE. After her father died many members of her family, including her husband, were put to death. When her brother Constantius II succeed to the throne Constance became directly involved in a political revolt using her political power to protect her own political interests. In 350 CE Magnentius, leader of the political opposition, offered to marry Constance and have her brother marry his daughter to create a powerful alliance. Constantius II turned this offer down, and instead gave Constance in marriage to their cousin Constantius Gallus, a young man several years her junior.
The marriage strengthened Constance's political position as the power behind what became a most ruthless tyranny. Behind the scenes she manipulated her impulsive husband into carrying out a cruel and sinister oppression of the people. She called for the murder of any who openly opposed her, and her husband foolishly had the massacre carried out. Hearing complaints about her, Constantius II summoned her back to Rome in 354 CE. She died on the way at Caeni Gallicani in Bithynia (Asia Minor).
The cause of her death was given as a sudden high fever of unknown cause, but foul play is suspected. Her body was sent back to Rome and entombed near Via Nomentana in a mausoleum built by her father. This mausoleum would later be named Santa Costanza in her honor, and a fictitious legend was created to memorialize her. Although venerated as a saint, the facts of her life prove Constance to have been an imperial tyrant. The mausoleum at the site of the Church of Santa Constanza survives largely intact, but only part of the wall of the former basilica survives. Her elaborately carved sarcophagus is on exhibit in the Vatican Museum.