In Norse mythology, Sinmara is a gýgr (giantess), usually considered a consort to the fiery jötunn Surtr, the lord of Muspelheim, but wife of Mimir. Sinmara is attested solely in the poem Fjölsvinnsmál, where she is mentioned alongside Surtr in one (emended) stanza, and described as keeper of the legendary weapon Lævateinn in a later passage. Assorted theories have been proposed about the etymology of her name, and her connection with other figures in Norse mythology.