In Norse mythology, Hel is the goddess who rules over the dead in her underworld realm.
Hel is a daughter of Loki and the giantess Angrboða. Odin sends her to govern the realm where many people who die from sickness or old age are said to go. The same word, Hel, is used for both the goddess and the place she rules, which can make translations confusing.
Medieval Norse sources portray Hel as an imposing figure, often described as partly living and partly corpse-like. Her realm is not identical to Valhalla, which is associated with Odin and selected warriors killed in battle. Nor is every dead person in Norse tradition assigned to one single destination; the sources describe several possible afterlife locations.
Modern English uses “hell” for a Christian theological concept, but the resemblance of the words does not mean that Hel’s mythology is simply the same doctrine. The Norse goddess and her realm belong to a different religious tradition.