Hydatius, also spelled Idacius (c. 400 – c. 469) was a late Western Roman writer and clergyman. The bishop of Aquae Flaviae in the Roman province of Gallaecia (almost certainly the modern Chaves, Portugal, in the modern district of Vila Real), he was the author of a chronicle of his own times that provides us with our best evidence for the history of Hispania in the 5th century.