Borghildr of Brálund, the first wife of Sigmundr and by him the mother of Hámundr and Helgi. She is the stepmother of Sinjlötli, whom she poisoned after he had caused the death of her brother Gunnar. The story is told in the short prose piece Frá dauða Sinfjötla found in the Codex Regius manuscript of the Prose Edda:
Borghild, Sigmund's wife, had a brother named Gunnar; but Sinfiötli her step-son and Gunnar both courted one woman, on which account Sinfiötli slew Gunnar. When he came home, Borghild bade him go away, but Sigmund offered the blood-fine, which it was incumbent on her to accept. At the funeral feast Borghild presented the beer: she took a large horn full of poison, and offered it to Sinfiötli; who, when he looked into the horn, and saw that there was poison in it, said to Sigmund: "the drink ferments!" Sigmund took the horn and drank up the contents. It is said that Sigmund was so strong that no poison could hurt him, either outwardly or inwardly; but that all his sons could endure poison outwardly. Borghild bore another horn to Sinfiötli, and prayed him to drink, when all took place as before. Yet a third time she offered him the horn, using reproachful words on his refusing to drink. He said as before to Sigmund, but the latter answered: "Let is pass through thy lips, my son." Sinfiötli drank and instantly died.
After his son's death, Sigmundr drove Borghildr away, and a little after she died.
- Frá dauða Sinfjötla.
- Helgakviða Hundingsbana I, 1.
- Völsunga saga, 10.