Domitius Modestus (Greek: Δομίτιος Μοδέστος; floruit 358–377) was a politician of the Roman Empire.
Modestus was comes Orientis from 358 to 362, succeeding to Nebridius and serving under the Emperors Constantius II and Julian.
While he was in Antioch, Julian appointed Modestus as praefectus urbi of Constantinople, an office he held from 362 to 363.
In 371, he was appointed president of a commission that was to judge some high officers who had been accused of practicing magic, in particular of having consulted a soothsayer to learn the name of the successor of Emperor Valens.
Ammianus Marcellinus and Gregory of Nazianzus accused him of base flattery towards the emperor, due to him being afraid for the succession and wanting to preserve his own power.