Divi filius is a Latin phrase meaning "son of a god", and was a title much used by the adopted son of Julius Caesar, his great-nephew Octavian, the future Emperor Augustus.

On 1 January 42 BC, nearly two years after the assassination of Julius Caesar on 15 March 44 BC, but before the final victory of the Second Triumvirate over the conspirators who had taken his life, the Roman Senate recognised him as a divinity. He was therefore referred to as Divus Iulius (the divine Julius), and his adopted son styled himself Divi filius (son of the deified one, son of the god). The fuller form, "divi Iuli filius" (son of the divine Julius) was also used.

Octavian used the title divi filius to advance his political position, finally overcoming all rivals for power within the Roman state. The title was for him "a useful propaganda tool", and was displayed on the coins that he issued.

Since Augustus himself (the title "Augustus" was officially conferred on Octavian in 27 BC) and some other Roman Emperors were deified after death, the title Divi Filius was also applied to some of Augustus's successors: Tiberius, Nero, and Domitian.

Gaius Julius Caesar (Classical Latin: [ˈɡaː.i.ʊs ˈjuː.lɪ.ʊs ˈkaj.sar], July 100 BC – 15 March 44 BC) was a Roman general and statesman and a distinguished writer of Latin prose. He played a critical role in the gradual transformation of the Roman Republic into the Roman Empire.

In 60 BC, Caesar, Crassus and Pompey formed a political alliance that was to dominate Roman politics for several years. Their attempts to amass power through populist tactics were opposed by the conservative elite within the Roman Senate^{[citation needed]}, among them Cato the Younger with the frequent support of Cicero. Caesar's conquest of Gaul, completed by 51 BC, extended Rome's territory to the English Channel and the Rhine. Caesar became the first Roman general to cross both when he built a bridge across the Rhine and conducted the first invasion of Britain.

These achievements granted him unmatched military power and threatened to eclipse Pompey's standing. The balance of power was further upset by the death of Crassus in 53 BC. Political realignments in Rome finally led to a standoff between Caesar and Pompey, the latter having taken up the cause of the Senate. Ordered by the Senate to stand trial in Rome for various charges, Caesar marched on Rome with one legion—legio XIII—from Gaul to Italy, crossing the Rubicon in 49 BC. This sparked a civil war from which he emerged as the unrivaled leader of the Roman world.