Flavius Caecina Decius Basilius (floruit 458-468) was a politician of the Western Roman Empire, Consul and twice Praetorian prefect of Italy.
Basilius belonged to the Italian nobility, and was member of the influential gens Caecina.
He was Praetorian prefect of Italy in 458, under Emperor Majorian. Emperor Libius Severus (461-465) honoured Basilius with the consulate of the year 463 (year in which he already was Patricius), nominating him also Praetorian prefect of Italy, a position Basilius held until 465.
The Gallic-Roman poet Sidonius Apollinaris, arrived in Rome in 467 to bring a petition of his people, tells that Basilius was one of the two most influential civil officers in Rome in the 460s, together with Gennadius Avienus. Sidonius asked Basilius' help, as he needed to bring his petition to Emperor Anthemius; Basilius suggested him to compose a panegyric in honour of the Emperor, in occasion of the beginning of Anthemius' consulate (January 1, 468). After the declamation, Basilius interceded with Anthemius for Sidonius, and the Emperor made the Gallic-Roman poet a senator, a Patricius and Praefectus urbi.
Basilius had three sons, all of them Consuls: Caecina Mavortius Basilius Decius (Consul in 486), Decius Marius Venantius Basilius (consul in 484), and Basilius iunior (consul in 480), identified with Caecina Decius Maximus Basilius.