In Norse mythology, Andvaranaut (Andvari's Gift), first owned by Andvari, is a magical ring that can make gold.
The mischievous godLoki tricked Andvari into giving him the Andvaranaut. In revenge, Andvari cursed the ring to bring misfortune and destruction to whoever possessed it. Loki quickly gave the cursed Andvaranaut to Hreidmar, King of the Dwarves, as reparation for having inadvertently killed Hreidmar's son, Ótr. Ótr's brother, Fafnir, then murdered Hreidmar and took the ring, turning into a dragon to guard it. Sigurd (Siegfried) later killed Fafnir and gave Andvaranaut to Brynhildr (Brünnehilde). Queen Grimhild of the Nibelungs then manipulated Sigurd and Brynhildr into marrying her children, bringing Andvaranaut's curse into her family.
In Thor (Marvel Comics) an adaption was done of the ring cycle, in which the ring appeared. Here it is much larger, meant to fit on all of Andvari's hand, though it fits on only one finger of the Giant Fafnir.
The story of Andvaranaut is one of the central themes of Richard Wagner's Der Ring des Nibelungen (The Ring of the Nibelung), although Wagner's story does not use the name "Andvaranaut."