Roman Emperor Constantine the Great elevates his youngest son Constans to the rank of Caesar.

Constantine I, also known as Constantine the Great, was a Roman emperor from AD 306 to 337 and the first Roman emperor to convert to Christianity. He played a pivotal role in elevating the status of Christianity in Rome, decriminalising Christian practice and ceasing Christian persecution. This was a turning point in the Christianisation of the Roman Empire. He founded the city of Constantinople and made it the capital of the Empire, which it remained for over a millennium.

Flavius Julius Constans, also called Constans I, was Roman emperor from 337 to 350. He held the imperial rank of caesar from 333, and was the youngest son of Constantine the Great.

Caesar is a title of imperial character. It derives from the cognomen of Julius Caesar. The change from being a surname to a title used by the Roman emperors can be traced to AD 68, following the fall of the Julio-Claudian dynasty. When used on its own, the title denoted heirs apparent, who would later adopt the title Augustus on accession. The title remained an essential part of the style of the emperors, and became the word for "emperor" in some languages, such as German and Slavic.