Thaumastus (born c. 400)[1] was a friend and uncle of Sidonius Apollinaris. His brother, the elder Apollinaris was born around 405[2] and was the praetorian prefect of Gaul under Valentinian III between 425 and 455.[3] Thaumastus and his brother were both sons of another Apollinaris, praetorian prefect of Gaul before 409[3] and were friends with his successor Decimus Rusticus. Thaumastus was associated with Tonantius Ferreolus in the impeachment of Arvandus.[4] He was the father of Eulalia, born in 425,[2] married before 450 to Flavius Probus, Roman Senator.
He seems to be a descendant of yet another Apollinaris, praetorian prefect of Gaul under Constantine II between 337 and 340.[3]