Nodens or *Nodons (reconstructed from the dative Nodenti or Nodonti) is a Celtic healing god worshipped in Ancient Britain. Although no physical depiction of him has survived, votive plaques found in a shrine at Lydney Park (Gloucestershire) indicate his connection with dogs, a beast associated with healing symbolism in antiquity. The deity is known in only one other location, in Cockersand Moss (Lancashire). He was equated on most inscriptions with the Roman god Mars (as a healer rather than as a warrior) and associated in a curse with Silvanus (a hunting-god). His name is cognate with that of later Celtic mythological figures, such as the Irish Nuada and the Welsh Nudd.
The philologist and author J. R. R. Tolkien was invited to investigate the Latin inscription, and scholars have noted several likely influences on his Middle-earth fantasy writings, including the Elvish smith, maker of Rings of Power, Celebrimbor, whose name, like that of Nuada's epithet Airgetlám, means 'Silver-hand'. Nodens appears, too, in H. P. Lovecraft's Cthulhu Mythos.
The theonym *Nodens or *Nodons is reconstructed from the attested dative singular Nodenti or Nodonti, which is derived from a Proto-Celtic stem *Nowdont-. It is a cognate (linguistic sibling from the same origin) of the Middle Irish Nuadu and the Middle Welsh Nudd (which turned into Lludd, apparently from an alliterative assimilation). The Irish genitives nodot and núada(i)t (perhaps 'hand, wrist or arm') also appear to be related. It suggests that Nōdonti was the original form, by showing the back vocalism of the Celtic suffix -ont-. The development from -ō- to -ū- in Brittonic languages dates back to the end of the 3rd century AD. An Old Breton name Nodent (modern Nuz) may also be added to the cognates, although the vocalism raises phonological difficulties.
The origin of the name remains obscure, scholar John Carey noting that "it seems at any rate safe to say that no etymology so far proposed can be accepted with full confidence".