Flavius Avitus Marinianus (fl. 423–448) was a politician of the Western Roman Empire during the reign of Honorius.

Avitus was praetorian prefect^[1] and consul in 423^[2] He is mentioned in the Gesta de purgatione Xysti III episcopi' in a list of aristocrats involved in the investigations against Pope Sixtus III. Although the Gesta has been long recognized as a later forgery, B.L. Twyman argued in 1970 that the list of aristocrats was taken from a later papal investigation concerning the deposition of bishop Celidonius by archbishop Hilarius of Arles.^[3] T.D. Barnes subsequently showed that the list was best explained as the product of "a writer of the sixth century [who] has deliberately mixed genuine and fictitious persons."^[4]

He had a wife, Anastasia, and a son, Rufius Praetextatus Postumianus (consul in 448);^[5] it is possible that Rufius Viventius Gallus was another son. Marinianus and his wife were Christians; at Pope Leo I's request, they restored the mosaic on the façade of the Old St. Peter's Basilica, as recorded by an inscription on the mosaic itself.^[6]