Aradia is one of the principal figures in the American folklorist Charles Godfrey Leland's 1899 work Aradia, or the Gospel of the Witches, which he believed to be a genuine religious text used by a group of pagan witches in Tuscany, a claim that has subsequently been disputed by other folklorists and historians. In Leland's Gospel, Aradia is portrayed as a messiah who was sent to Earth in order to teach the oppressed peasants how to perform witchcraft to use against the Roman Catholic Church and the upper classes.

The folklorist Sabina Magliocco has theorised that prior to being used in Leland's Gospel, Aradia was originally a supernatural figure in Italian folklore, who was later merged with other folkloric figures such as sa Rejusta of Sardinia.

Since the publication of Leland's Gospel, Aradia has become "arguably one of the central figures of the modern pagan witchcraft revival" and as such has featured in various forms of Neopaganism, including Wicca and Stregheria, as an actual deity.Raven Grimassi, founder of the Wiccan-inspired tradition of Stregheria, claims that Aradia was a historical figure named Aradia di Toscano, who led a group of "Diana-worshipping witches" in 14th-century Tuscany.