Arbitio

Arbitio (fl. 354-366) was a Roman general (magister militum) and Consul who lived in the middle of the 4th century.

In the Reign of Constantius II

He was a general of Constantine I and reached the highest military positions in the Roman army under his son and successor Constantius II and became magister equitum (commander of the cavalry). In 355 he was made consul together with Quintus Flavius Maesius Egnatius Lollianus.

Arbitio was a well trusted courtier of Constantius and some modern historians have suggested he was his military strongman.

Arbitio intrigued against Claudius Silvanus, Ursicinus and Barbatio and played a role in their downfalls. Historian Ammianus Marcellinus says he was "keen and eager in plotting treachery", and describes him as "fickle flatterer" to Constantius II.

In the Reign of Julian

After the death of Constantius in 361, he was appointed chairman of the Chalcedon tribunal by the new Emperor Julian. In this function he was responsible for the conviction of Paulus Catena and many ministers and followers of Constantius. Arbitio did not take part in the Persian campaign of Julian, but instead retired to live as a private citizen.