Ulpia Severina (fl. 3rd century) was a Roman Empress, the wife of the emperor Aurelian. There is evidence that she reigned in her own right for some period after Aurelian's death in 275, which would make her the only woman to have ruled over the entire classical Roman Empire by her own power. Very little is known about her, as there are no literary sources mentioning her existence. Almost everything known about her, including her name, is gathered from coins and inscriptions.
Nothing certain is known of Ulpia Severina before her marriage to Aurelian. It has been suggested that she was the daughter of Ulpius Crinitus, a figure appearing in the Historia Augusta. This Ulpius is said to have been a descendant of the line of Trajan and to have supported and adopted Aurelian. However, the Historia Augusta is notoriously unreliable, and the story, and perhaps Ulpius himself, may have been invented by propagandists trying to connect Aurelian with the "Good Emperor" Trajan. Some scholars believe that Ulpia Severina was from Dacia, where the nomen Ulpius was common due to the influence of Trajan (Marcus Ulpius Traianus).
At any rate, Ulpia Severina married Aurelian probably before he became emperor in 270. It is known they had a daughter. According to coinage depicting her, Ulpia gained the title Augusta in the autumn of 274, though it is possible she had the title even before that. She also received the titles of Pia ("pious") and mater castrorum et senatus et patriae ("mother of the barracks (armies), senate, and country").
There is considerable numismatic evidence for Ulpia Severina ruling in her own right between the death of Aurelian and the election of Marcus Claudius Tacitus. Sources mention an interregnum between Aurelian and Tacitus, and some of Ulpia's coins appear to have been minted after Aurelian's death. As such she may have been the only woman to rule over the whole Roman Empire in her own power.