[of the silver hand/arm]. King of the mythical Tuatha Dé Danann who leads his people into Ireland but is later disqualified from kingship because of the ‘blemish’ of his severed arm. Dispute over the succession to replace him dominates the beginning of the action of Cath Maige Tuired [The (Second) Battle of Mag Tuired]. The initial conception of this deeply mysterious character apparently pre-dates the narratives of the Mythological and Fenian Cycles. None the less, he appears frequently in early Irish tradition, often taking markedly different aspects, perhaps also taking different epithets as well. His early British cognate is Nodons, worshipped at the Romano-British shrine of Lydney Park; and he clearly resembles the Welsh Nudd, more certainly derived from Nodons, who sometimes bears the epithet Llaw Ereint [silver hand].
In earliest Irish tradition Nuadu is associated with the Boyne as the consort of the river's eponym Boand under his pseudonym Nechtan (1); under yet another pseudonym, Elcmar, he has an affair with her. In the south of Ireland he was so much associated with the Eóganacht dynasty that its leading member, Eógan Mór, has an alternative name of Mug Nuadat [servant of Nuadu]. Together with these incarnations, we also find Nuadu as a member of the Tuatha Dé Danann, bringing the stone of Fál to Ireland. His sword is one of the four treasures of the Tuatha Dé Danann. But Nuadu's kingship is interrupted, as he relinquishes the sacred office twice. First, it is because he no longer meets the criterion of physical perfection, a rule of sovereignty. In the First Battle of Mag Tuired, a Fir Bolg warrior named Sreng severs Nuadu's arm, but his Tuatha Dé comrades carry him from the field. On the next day Nuadu challenges Sreng to tie up his own right arm to ensure a fair fight, but Sreng refuses. To prevent a fatal injury to Nuadu, the Tuatha Dé then offer Sreng and the Fir Bolg the province of Connacht, which they accept. The ill-starred Bres then becomes leader of the Tuatha Dé Danann, but after seven years Dian Cécht makes a silver arm for Nuadu, and he is restored to the kingship for another twenty years. In his second reign Nuadu is daunted by the terrible power of Balor and is thus replaced by Lug Lámfhota, who brings victory to the Tuatha Dé Danann.
Nuadu may also play a role in the Fenian Cycle, perhaps confused with Nuadu Necht, the Leinster ancestor-deity. He is thought to have married Eithne (1) (elsewhere the mother of Lug Lámfhota) to found the family line that forms the maternal ancestry of Fionn mac Cumhaill. Additionally, Nuadu was thought to be the original owner of the fortress at the Hill of Allen [Almu, etc.], also attributed to Tadg mac Nuadat, a ‘son’ who may be an alias for the father. Nuadu is one of three prophets of pre-Christian religion, along with Goibniu and the shadowy Mathu. Another attributed consort is Fea, a war-goddess. Oral tradition has him buried at Ailech in Co. Donegal.