- This article is about the figure in Norse mythology, for C. S. Friedman's fictional world, see Erna (planet). For eRNA (efference RNA), see Non-coding RNA. For a military exercise in Estonia, see Erna Raid.
In Norse mythology, Erna was the mother of eleven sons by Jarl, the ancestors of the race of warriors in Norse society. Her father was Hersir, a tribal chief.
- Dugdale-Pointon, TDP. (21 March 2001), Hersir, Viking, *http://www.historyofwar.org/articles/weapons_hersir.html