Orcus was a god of the underworld, punisher of broken oaths in Etruscan and Roman mythology.

The Romans sometimes conflated Orcus with other underworld gods such as Pluto, Hades, and Dis Pater.

The name "Orcus" seems to have referred specifically to the malicious and punishing side of the ruler of the underworld, as the god who tormented evildoers in their afterlife.

He survived as a folk figure into the Middle Ages, and aspects of his worship may have been transmuted into the wild man festivals held in rural parts of Europe through the modern era.

An early example of an orco appears in Ludovico Ariosto's Orlando Furioso (1516), as a bestial, blind, tusk-faced monster inspired by the Cyclops of the Odyssey.