Which Norse Valkyrie was the wife of Gunnar and betrayed Sigurd?

The Norse Valkyrie who became Gunnar’s wife and helped bring about Sigurd’s death was Brynhild. In the Völsunga saga, she is a formidable valkyrie associated with a ring of fire and a vow to marry only a fearless hero.

Brynhild first loves Sigurd, the dragon-slayer, after he awakens her. Through deception and magic, however, Sigurd helps Gunnar win her: Sigurd rides through the flames in Gunnar’s form, then places a sword between himself and Brynhild so their marriage bed is not consummated. Brynhild consequently marries Gunnar while believing that he fulfilled her challenge.

The deception is exposed when Brynhild and Gudrun quarrel. Gudrun reveals that Sigurd—not Gunnar—crossed the flames, and Brynhild recognizes the ring Sigurd had taken from her. Seeking revenge, Brynhild urges Gunnar’s family to have Sigurd killed. In the Völsunga saga, she then takes her own life and is burned on the same funeral pyre as Sigurd.

Sigrdrífa is sometimes treated as the same figure in parts of the Eddic tradition, which causes confusion, while Gudrun is Sigurd’s wife and Gunnar’s sister—not Brynhild’s name.