Tacitus (200-276 CE) was born in Interamna (Terni), Italia, and worked for much of his long life in various civil offices, including a term as consul in 273, earning him much universal respect. When Aurelian was assassinated by the Praetorian Guard, Tacitus was chosen as his successor after a brief interregnum by the Roman Senate, the last time the Senate would elect an emperor.

Tacitus' brief reign saw him fight against barbarian mercenaries that had been serving under Aurelian but had broken away to plunder several towns in the Eastern Roman provinces after the previous emperor's death. He then turned his attention to a resurgent Alammanic and Frankish invasion in the province of Gaul, but died of fever on the march westwards. Some other accounts claim that he was assassinated instead, after having appointed one of his own relatives to an important command in Syria. His reign barely lasted nine months.