Hagen (German form) or Högni (Old NorseHǫgni, often anglicized as Hogni) is a Burgundian warrior in tales about the Burgundian kingdom at Worms. Hagen is often identified as a brother or half-brother of King Gunther (Old Norse Gunnarr).
In the Nibelungenlied, he is called Hagen of Tronje (perhaps Drongen in Ghent). In German tradition, Hagen is especially grim, implacable, and violent and in two accounts one-eyed. According to the Thidreks saga, Hagen was not fully human, being fathered by an elf on the king's wife. In these accounts, it is Hagen who kills the hero Siegfried during a hunt, wounding him on the only part of his body which was not invulnerable. This version of the character appears in Wagner'sDer Ring des Nibelungen (in this version, Hagen kills Gunther in a dispute over the ring and drowns trying to take it from the Rhinemaidens). In Norse tradition, Hagen's counterpart Högni is less extreme and the actual slayer of Sigurd (the Norse counterpart to Siegfried) is Gutthorm, a younger brother of Gunnar and Högni. But Gutthorm does so when egged on by his elder brothers.
In German accounts, Gunther and Hagen are the last survivors of the fall of the Nibelungs. Hagen refuses to reveal the hiding place of the Nibelung treasure to Kriemhild as long as his king Gunther lives. When Gunther is slain, the mortally-wounded Hagen continues his refusal with sure knowledge that Gunther cannot now weaken and betray the secret. In Norse accounts, however, it is Gunnar who refuses to tell the secret to Attila the Hun as long as Högni lives, and so brings about Högni's death.
In Atlamál, Hniflung a son of Hagen/Högni avenges his father's death and the deaths of his kin together with his aunt Guðrún. This work also states that Hogni had a wife named Kostbera and two other sons: Solar and Snævar. The Drap Niflunga mentions a fourth son named Gjuki (named after Hogni's father).