Licinius (263-325) was born to a peasant family and was a close childhood friend of future emperor Galerius; becoming a close confidante to Galerius and entrusted with the eastern provinces when Galerius went to deal with the usurper Maxentius. Galerius elevated Licinius to co-emperor; Augustus in the West; in 308; though he personally had control over the eastern provinces.

After emperors Maxentius and Maximinus II formed an alliance; Licinius was forced to enter into a formal agreement with Constantine I; marrying his half-sister Flavia Julia Constantia. He fought against Maximinus' forces and finally killed him in 313; while Constantine had defeated Maxentius in 312.

The two divided the Roman Empire between them; but civil war soon erupted a year later in 314. The two emperors would constantly war against each other; then make peace before restarting conflict again for the next few years. Licinius was finally defeated for good in 324; with only the pleas of his wife; Constantine's sister; saving him. Licinius was then hanged a year later in 325; accused by Constantine of conspiring to stir revolt among the barbarians.