The king of Närke, south central Sweden. He had two sons and a daughter, Böðvildr. He desired Völundr's gold and commanded his men to capture the smith. He gave one of the smith's golden rings to his daughter while he himself appropriated Völundr's sword. He then had Völundr hamstrung and imprisoned on the small island of Sævarstöð, where he was made to forge for the king all kinds of jewelry work.
Völundr exacted a terrible vengeance on Níðuðr's family for what had been done to him. He first killed Níðuðr's two young sons and fashioned their skulls into silver goblets. Out of their eyes he formed precious stones and gave these to Níðuðr's wife, and out of their teeth he made two breast-ornaments for Böðvildr. When Böðvildr came to the island to have her ring repaired, Völundr plied her with beer and raped her. Fearing her father's wrath, she fled from the island. Völundr then made for himself a pair of wings, and flew to Níðuðr's dwelling.
Níðuðr, who had slept little since his two sons were slain, asked Völundr what had happened to them. Völundr first made Níðuðr swear that he would not harm his wife Hervör, and then told the king precisely what had been done to his family. Níðuðr was greatly affected by the smith's words. After Völundr had left, Níðuðr commanded one of his thralls to bring him Böðvildr, who confirmed that she had lain with Völundr and now carried his child.
He appears as Niðung in Þiðrekssaga. He was the king of Jutland. The master smith Velent becomes a servant at his court.