For the Högni of the Heimskringla and the legends of Helge Hundingsbane, see Högne.

Hagen (German form) or Högni (Old Norse Hǫgni, 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 (Anglicized Old Norse Gunnar).

In the Nibelungenlied he is called Hagen of Tronje (perhaps Drongen in Ghent). In German tradition Hagen is especially grim, implicable, 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 indestructible. In Norse tradition Hagen's counterpart Högni is less extreme and the actual slayer of Sigurd (the Norse cunterpart 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 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 as long as Högni lives, and so brings about Högni's death.

In some tales a posthumous son of Hagen/Högni avenges his father's death and the deaths of his kin.