Quintillus (212-270) was born at Sirmium to a low-born family, only coming to any prominence when his brother Claudius II Gothicus became emperor in 268. When Claudius II died two years later in 270, Quintillus was declared his successor, either by the Roman Senate or by his brother's soldiers.

The exact dates and length of Quintillus' reign are contradictory, lasting anything from 17 to 177 days. Similarly, the cause of his death is unknown, with some sources stating that he was murdered by his own soldiers for his strict military discipline, while others report him being killed in battle against rival claimant Aurelian. Still some sources claim that he committed suicide.

What few records remain of him claim Quintillus to be a moderate and capable ruler, a champion of the Senate and spiritual successor to previous Emperors Galba and Pertinax.