Gaius Sollius Modestus Sidonius Apollinaris (c.430 - after 479) was Urban Prefect of Rome in 470, and bishop of Auvergne afterwards until his death. Sidonius was a major Gaulic aristocrat, whose life and friendships put him in the center of 5th century Roman affairs. He married Papianilla, daughter of Avitus who was later Roman Emperor. Sidonius was also acquainted with the Visigothic kings who ruled during his lifetime. Some, like Theodoric II, he was on good terms with; others, like Euric who had him imprisoned during his bishopric for his pro-Roman views, he was on less favorable terms with.

After his career in Imperial service, he was elected bishop of Clermont-Ferrand sometime around 469 or 470. Not a religious man, his election was probably due more to his influential contacts, and his tireless efforts on preserving his corner of Gaul for the Roman Empire.

Sidonius' writings are an invaluable source of information for events and attitudes during his adult lifetime. He wrote several panegyrics, after the fashion of Claudian, which document several important political events. Carmen 7 is a panegyric to his father-in-law Avitus on his inauguration as emperor. Carmen 5 is a panegyric to Majorian, which offers evidence that Sidonius was able to overcome the natural suspicion and hostility towards the man who was responsible for the death of his father-in-law. Carmen 2 is a panegyric to the emperor Anthemius, part of Sidonius' efforts to be appointed Urban Prefect of Rome. Especially a letter of Sidonius to Riothamus, the King of Brettones (~460) is of interest. It is a significant evidence that a King or leader with power was existent in the historical time frame of King Arthur.

Sidonius' relations have been traced over several generations, from his paternal grandfather's time in the narrative of a family's fortunes from prominence in late Roman time into subsequent decline in the 6th century under the Franks.