Numerian was Roman emperor from 283 to 284 with his older brother Carinus. They were sons of Carus, a general raised to the office of praetorian prefect under Emperor Probus in 282.

The Roman emperor was the ruler and monarchical head of state of the Roman Empire, starting with the granting of the title augustus to Octavian in 27 BC. The term "emperor" is a modern convention, and did not exist as such during the Empire. Often when a given Roman is described as becoming emperor in English, it reflects his taking of the title augustus and later basileus. Another title used was imperator, originally a military honorific, and caesar, originally a surname. Early emperors also used the title princeps alongside other Republican titles, notably consul and pontifex maximus.