In Neil Gaiman’s novel Norse Mythology, Thor’s hammer is named Mjollnir.
Gaiman’s 2017 book retells stories drawn mainly from the Poetic Edda and Prose Edda. Mjollnir is Thor’s principal weapon and is associated with thunder, protection, and the defense of the gods and humans.
The hammer is forged by the dwarfs Sindri and Brok, although Loki’s interference causes its handle to be shorter than intended. Despite that flaw, Mjollnir remains exceptionally powerful and returns to Thor after being thrown. It can also be used in rituals connected with consecration and resurrection.
The spelling varies in English because the name is transliterated from Old Norse. “Mjolnir” and “Mjöllnir” are common forms, while “Mjollnir” is widely used in English reference works and in Gaiman-related listings.