Faustina (fl. 361 – 366) was an Empress of the Roman Empire and third wife of Emperor Constantius II. The main source for her biography is the account of historian Ammianus Marcellinus. Her origins and other names are unknown.
Constantius married her in Antioch in 361, after the death of his second wife, Eusebia in 360. Ammianus simply reports that the marriage took place while Constantius was wintering in Antioch, taking a break from the ongoing Roman–Persian Wars. "At that same time Constantius took to wife Faustina, having long since lost Eusebia".
She was pregnant when Constantius died on 5 October 361 and later gave birth to their posthumous daughter, Flavia Maxima Constantia, the only child of the emperor. Constantia later married Emperor Gratian.
On 28 September 365 Faustina was present when Procopius received the insignia of the imperial rites in Constantinople. Faustina and her little daughter's presence suggested that Procopius was the rightful heir of the Constantinian dynasty which was still held in reverence.
Ammianus considers that Procopius having Faustina and Constantia by his side increased the loyalty of the people to his cause:
"Valens called forth his troops and joining with him Lupicinus and a strong force of auxiliaries, he hastened to Pessinus, formerly a town of Phrygia, now of Galatia. Having safely garrisoned this place in order to suffer no surprise in those parts, he marched along the foot of the lofty mountain called Olympus, and over rocky paths, towards Lycia, planning to attack Gomoarius, while he loitered there half asleep. But he [Valens] was met with general and obstinate resistance, for this reason in particular — that his enemy (as has been mentioned) both on the march and when they were almost in battle array, carried about with him in a litter the little daughter of Constantius, and her mother Faustina; and thereby had inflamed the passions of the soldiers to fight more bravely in defence of the imperial stock, with which he claimed that he himself was connected." 
After the Battle of Thyatira and the fall of Procopius in 366, Faustina passes out of sight.
|Roman Empress consort
- Prosopography of the Later Roman Empire, vol. 1
- "The Roman History of Ammianus Marcellinus, vol. 2, Book 21, chapter 6. 1940 translation". Penelope.uchicago.edu. Retrieved 2011-04-11.
- "Constantius, therefore, having reached Antiochia by forced marches, intending (as was his custom) eagerly to encounter civil disturbances at their outset, and having made all his preparations, was in immoderate haste to set out, although many opposed it, but only by murmurs; for no one dared openly to dissuade or to forbid him. When autumn was already waning he began his march, and on coming to a suburban estate called Hippocephalus, distant three miles [4.5 km] from the city, he saw in broad daylight on the right side of the road the corpse of a man with head torn off, lying stretched out towards the west. Terrified by the omen, although the fates were preparing his end, he kept on with the greater determination and arrived at Tarsus. After this followed the last mournful call to the deceased, and grief and wailing broke out; then those who held the first rank in the royal court considered what they should do, or what they ought to attempt. And after a few had been sounded secretly as to the choice of an emperor, at the suggestion of Eusebius (as was reported), whom the consciousness of his guilt pricked, since Julian's nearness made an attempt at revolution inadvisable, Theolaifus and Aligildus, at that time counts, were sent to him, to report the death of his kinsman, and beg him to lay aside all delay and come to take over the Orient, which was ready to obey him. However, rumour and an uncertain report had it that Constantius had made a last will, in which (as I have said) he wrote down Julian as his heir and gave commissions and legacies to those who were dear to him. Now he left his wife with child, and the posthumous daughter to whom she afterwards gave birth was called by his name, and when she grew up was united in marriage with Gratianus." - "The Roman History of Ammianus Marcellinus, vol. 2, Book 21, chapter 15. 1940 translation". Penelope.uchicago.edu. Retrieved 2011-04-11.
- "For some divisions of cavalry and infantry which had been raised for the campaign in Thrace passed that way; they were received courteously and generously, and when they were all united in one body, there was already the appearance of an army. Eager for the riches that were promised, they swore allegiance to Procopius with dire penalties for disloyalty, promising to stand by him and protect him with their lives. There was found, besides, a very favourable means of winning them over, namely, that Procopius took in his arms the little daughter of Constantius, whose memory they honoured, and carried her about, claiming kinship with the former emperor. And he gained another timely advantage in that Faustina, the girl's mother, happened to be present when he had received some insignia forming a part of the imperial adornment." - "The Roman History of Ammianus Marcellinus, vol. 2, Book 26, chapter 7. 1940 translation". Penelope.uchicago.edu. Retrieved 2011-04-11.
- "The Roman History of Ammianus Marcellinus, vol. 2, Book 26, chapter 9. 1940 translation". Penelope.uchicago.edu. Retrieved 2011-04-11.