In Norse mythology, Gudrun, who is called Kriemhild in the Nibelungenlied, was the sister of Gunnar. She is loosely based on the princess Ildico in her role as the wife of Attila the Hun. Gudrun fell in love with Sigurd, who didn't care for her, because he was in love with the valkyrie Brynhild, to whom he gave the ring Andvarinaut.
In another version, Brynhild is imprisoned inside a ring of fire as a punishment by Odin. Sigurd had already gone through the fire once and promised his marriage to Brynhild, but he is cursed by Andvarinaut and bewitched, and switched bodies with Gunnar for a time. In the guise of Gunnar, he rides through the fire and Brynhild is forced to marry Gunnar.
Gudrun's mother Grimhild, who is called Ute in the Nibelungenlied, gave her a love-potion and Sigurd forgot his love for Brynhild. Gunnar allowed a marriage between Gudrun and Sigurd under the condition, that Sigurd would win the hand of Brynhild for him. Sigurd succeeded in doing so; taking the shape of Gunnar, he took Andvarinaut from Brynhild and gave it to Gudrun as his morning gift. Both Queens, Gudrun and Brynhild, were married on the same day.
After the death of Sigurd, Byrnhild had his three year old son Sigmund murdered. Gudrun later married the king Atle (loosely based on Attila the Hun), who is in the northern version responsible for the death of her whole family, who did inherit the name Völsunge/Niebelungen from the gold. The queen took revenge for her family by killing her and Atli's two sons Erp and Eitil and serving them as dinner to him at a feast in his hall. Later, when he was solidly drunk, she broke the news to him:
She then set fire to the hall of Attila, thus killing him along with and all of his men. Subsequently, she tried to drown herself by jumping into the sea with an armful of stones, but the waves found her revenge fitting, and instead carried her to Sweden, where she married another king, Jónakr, with whom she had three sons Hamdir, Sörli and Erp.
In the southern version Gudrun, here Kriemhild, kills her brothers to get the Niebelungen-gold back, for this she is killed by Dietrich von Bern.