Julius Julianus (fl. 315–325) was a politician of the Roman Empire, related to the Constantinian dynasty.
He served Licinius as praetorian prefect from at least spring 315 to September 324, until Constantine I definitively defeated Licinius. However, the fall of Licinius did not mark the end of Julianus' career, as Constantine had praised Julianus' administration of the State and chose him, in 325, as suffect to replace a consul fallen in disgrace, Valerius Proculus.
He was the father of Basilina, wife of Constantine's half brother Julius Constantius and mother of Emperor Julian, and of the mother of Procopius; he was probably related to Eusebius of Nicomedia.