Bassianus (died 316) was a Roman senator and a member of the Constantinian dynasty.
In 315 Constantine I went to Italy, where Bassianus was to be married to his half-sister Anastasia. The marriage never took place. The choice of Bassianus is probably to be understood in light of the fact that Bassianus' brother, Senecio, was a high official (probably dux limitis) in service of Licinius, Constantine's colleague in the East, and thus this marriage strengthened the bond between the two augusti.
The next year, in 316, Constantine sent his half-brother Julius Constantius, to Licinius at Sirmium, with the proposal of elevating Bassianus to the rank of caesar and with power over Italy. Licinius refused to acknowledge the appointment; furthermore, he told Senecio to contact his brother and have him kill Constantine, take arms and conquer Italy for Licinius. The conspiracy was discovered and Bassianus arrested and put to death. Constantine asked Licinius to hand him Senecio, but Licinius refused and overthrew his colleague's statues at Emona, on the border between the two spheres of influence; these events led to the outbreak of hostilities between Constantine and Licinius, an episode of civil war known as the bellum Cibalense.
- Odahl, p. 144.
- According to Eusebius of Caesarea (Vita Constantini, 1.47.1), Constantine discovered the assassination plot thanks to a vision sent by God.
- François Chausson, Stemmata aurea: Constantin, Justine, Théodose, L'erma di Bretschenider, 2007, ISBN 88-8265-393-5, p. 127-129.
- Origo Constantini, 5,14–15.
- Eusebius of Caesarea, Vita Constantini, 1.47.1
- Zosimus, Historia nea, II.18–20.