Pluto (Latin: Plūtō; Greek: Πλούτων, Ploútōn) is the ruler of the underworld in classical mythology. The earlier name for the god was Hades, which became more common as the name of the underworld itself. In ancient Greek religion and mythology, Pluto represents a more positive concept of the god who presides over the afterlife. Ploutōn was frequently conflated with Ploutos, the Greek god of wealth, because mineral wealth was found underground, and because as a chthonic god Pluto ruled the deep earth that contained the seeds necessary for a bountiful harvest. The name Ploutōn came into widespread usage with the Eleusinian Mysteries, in which Pluto was venerated as both a stern ruler and a loving husband to Persephone. The couple received souls in the afterlife and are invoked together in religious inscriptions, being referred to as Plouton and as Kore respectively.\

Pluto and Hades are the same figure. In Greek cosmogony, the god received the rule of the underworld in a three-way division of sovereignty over the world, with his brother Zeus ruling the sky and his other brother Poseidon sovereign over the sea. His central narrative in myth is of him abducting Persephone to be his wife and the queen of his realm. Plouton as the name of the ruler of the underworld first appears in Greek literature of the Classical period, in the works of the Athenian playwrights and of the philosopher Plato, who is the major Greek source on its significance. Under the name Pluto, the god appears in other myths in a secondary role, mostly as the possessor of a quest-object, and especially in the descent of Orpheus or other heroes to the underworld.

Plūtō ([ˈpluːtoː]; genitive Plūtōnis) is the Latinized form of the Greek Plouton. Pluto's Roman equivalent is Dis Pater, whose name is most often taken to mean "Rich Father" and is perhaps a direct translation of Plouton. Pluto was also identified with the obscure Roman Orcus, like Hades the name of both a god of the underworld and the underworld as a place. Pluto (Pluton in French and German, Plutone in Italian) becomes the most common name for the classical ruler of the underworld in subsequent Western literature and other art forms.