Flavius Julius Constantius (d. September, 337) was a son of Western Roman Emperor Constantius Chlorus and his second wife Flavia Maximiana Theodora. He was a younger half-brother of Roman Emperor Constantine I.
His father died on July 25, 306 when Julius Constantius was either a child or an adolescent. He is considered to have spent much of the 300s, 310s and 320s under virtual house arrest in Tolosa , Gallia Narbonensis, Gaul, Western Roman Empire under orders of his brother.
He first married Galla, sister of both Vulcacius Rufus and Neratius Cerealis. They had three known children.:
He married for a second time to Basilina, daughter of Caeionius Iulianus Camenius. They only had one known son:
His half-brother favored Julius Constantius by naming him a patrician and by appointing him consul in 335. When Constantine died on May 22, 337, Julius Constantius was in position to claim the throne for himself. He was murdered within months of Constantine's death along with most males of their family.
Only five males survived the series of assassinations. His nephews and new Roman Emperors Constantine II, Constantius II and Constans along with his two own young sons. Constantius II is suspected to have ordered the assassination of his uncle.