In ancient Greek religion and myth, Pluto (Πλούτων, Ploutōn) was a name for the ruler of the underworld; the god was also known as Hades, a name for the underworld itself. This deity has two major myths: in Greek cosmogony, he received the rule of the underworld in a three-way division of sovereignty over the world, with his brothers Zeus ruling Heaven and Poseidon the Sea; and he abducts Persephone to be his wife and the queen of his realm. In other myths, he plays a secondary role, mostly as the possessor of a quest-object.

The name Ploutōn was frequently conflated with that of Plutus (Πλοῦτος, Ploutos), a 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. Ploutōn became a more positive way to talk about the ruler of the underworld, and the name was popularized through the mystery religions and philosophical systems influenced by Plato, the major Greek source on its meaning.

Pluto (genitive Plutonis) is the Latinized form of the Greek Ploutōn. Pluto's Roman equivalent is Dis Pater, whose name is most often taken to mean "Rich Father." 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. The name Pluto is sometimes used for the ruler of the dead in Latin literature, leading some mythology handbooks to assert misleadingly that Pluto was the Roman counterpart of Hades, rather than an adopted Greek name identified with Dis Pater or Orcus. Pluto (French Pluton and Italian Plutone) is commonly used as the name of the classical ruler of the underworld in subsequent Western literature and other art forms.