Valerian was Roman emperor from 253 to spring 260 AD. Valerian is known as the first Roman emperor to have been taken captive in battle, captured by the Persian emperor Shapur I after the Battle of Edessa, causing shock and instability throughout the Roman Empire. The unprecedented event and the unknown fate of the captured emperor generated a variety of different reactions and "new narratives about the Roman Empire in diverse contexts".

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.