Dīs Pater (pronounced [diːs ˈpa.tɛr]) was a Roman god of the underworld. Dis was originally associated with fertile agricultural land and mineral wealth, and since those minerals came from underground, he was later equated with the chthonic deities Pluto (Hades) and Orcus.

Dīs Pater was commonly shortened to simply Dīs and this name has since become an alternative name for the underworld or a part of the underworld, such as the City of Dis of Dante's The Divine Comedy, which comprises Lower Hell.

It is often thought that Dīs Pater was also a Celtic god. This confusion arises from the second-hand citation of one of Julius Caesar's comments in his Commentaries on the Gallic Wars (VI:18), where he says that the Gauls all claimed descent from Dīs Pater. However, Caesar's remark is a clear example of interpretatio Romana: what Caesar meant was that the Gauls all claimed descent from a Gaulish god that reminded him of the Roman Dīs Pater, a scholia on the Pharsalia equates Dis Pater with Taranis, the chief sky deity in the Gaulish religion.^[1] Different possible candidates exist for this role in Celtic religion, such as Gaulish Sucellus, Irish Donn and Welsh Beli Mawr, among others.

In De Natura Deorum, Cicero derives the name of Dīs Pater from the Latin dives ("wealth, riches"), suggesting a meaning of "father of riches" (Pater is "father" in Latin), directly corresponding to the name Pluto, Pluto simply being how Plouton (Πλούτων in Greek) is spelled in Latin. (Plouton, meaning "the rich one", was a title bestowed upon the Greek god Hades). According to some 19th century authors, many of Cicero's etymological derivations are not to be taken seriously, and may indeed have been intended ironically;^[2] however, this particular derivation of Cicero's has been accepted by some contemporary authors, some even suggesting that Dīs Pater is a direct loan translation of the Greek Plouton.^[3]

Alternatively, he may be a secondary reflex of the same god as Jupiter (Proto-Indo-European Dyeus Ph₂ter or "Zeus-Pater").

Dīs Pater eventually became associated with death and the underworld because mineral wealth such as gems and precious metals came from underground, wherein lies the realm of the dead, i.e. Hades' (Pluto's) domain.

In being conflated with Pluto, Dīs Pater took on some of the latter's mythological attributes, being one of the three sons of Saturn (Greek Cronus) and Ops (Greek Rhea), along with Jupiter (Greek Zeus) and Neptune (Greek Poseidon). He ruled the underworld and the dead beside his wife, Proserpina (Greek Persephone).^[4] In literature, Dīs Pater's name was commonly used as a symbolic and poetic way of referring to death itself.

In 249 BC and 207 BC, the Roman Senate under senator Lucius Catellius ordained special festivals to appease Dīs Pater and Proserpina. Every hundred years, a festival was celebrated in his name. According to legend, a round marble altar, Altar of Dīs Pater and Proserpina (Latin: Ara Ditis Patris et Proserpinae), was miraculously discovered by the servants of a Sabine called Valesius, the ancestor of the first consul. The servants were digging in the Tarentum on the edge of the Campus Martius to lay foundations following instructions given to Valesius's children in dreams, when they found the altar 20 feet (6 m) underground. Valesius reburied the altar after three days of games. Sacrifices were offered to this altar during the Ludi Saeculares or Ludi Tarentini. It may have been uncovered for each occasion of the games, to be reburied afterwards, a clearly chthonic tradition of worship. It was rediscovered in 1886–87 beneath the Corso Vittorio Emanuele in Rome.^[5][6]

In addition to being considered the ancestor of the Gauls, Dīs Pater was sometimes identified with the Sabine god Soranus. In southern Germany and the Balkans, Dīs Pater had a Celtic goddess, Aericura, as a consort. Dīs Pater was rarely associated with foreign deities in the shortened form of his name, Dis.^[7]