Gaius Julius Hyginus^{[pronunciation?]} (ca. 64 BC – AD 17) was a Latin author, a pupil of the famous Cornelius Alexander Polyhistor, and a freedman of Caesar Augustus. He was by Augustus elected superintendent of the Palatine library according to Suetonius' De Grammaticis, 20. It is not clear whether Hyginus was a native of Spain or of Alexandria.

Suetonius remarks that he fell into great poverty in his old age, and was supported by the historian Clodius Licinus. Hyginus was a voluminous author: his works included topographical and biographical treatises, commentaries on Helvius Cinna and the poems of Virgil, and disquisitions on agriculture and bee-keeping. All these are lost.

Under the name of Hyginus there are extant what are probably two sets of school notes abbreviating his treatises on mythology; one is a collection of Fabulae ("stories"), the other a "Poetical Astronomy".

The lunar crater Hyginus and the minor planet 12155 Hyginus are named after him.

Fabulae consists of some three hundred very brief and plainly, even crudely told myths and celestial genealogies, made by an author who was characterized by his modern editor, H. J. Rose. as adulescentem imperitum, semidoctum, stultum—"an ignorant youth, semi-learned, stupid"—but valuable for the use made of works of Greek writers of tragedy that are now lost. Arthur L. Keith, reviewing H. J. Rose's edition (1934) of Hygini Fabulae for the Loeb Classical Library wondered "at the caprices of Fortune who has allowed many of the plays of an Aeschylus, the larger portion of Livy's histories, and other priceless treasures to perish, while this school-boy's exercise has survived to become the pabulum of scholarly effort." Hyginus' compilation represents in primitive form what every educated Roman in the age of the Antonines was expected to know of Greek myth, at the simplest level. The Fabulae are a mine of information today, when so many more nuanced versions of the myths have been lost.