Sif (Old Norse: Sif) is the wife of Thor, described in Gylfaginning as a prophetess (spákona) and notable above all for her magnificent golden hair. Her most prominent mythological episode involves the cutting of her hair: Loki cuts off all of Sif’s hair while she sleeps. When Thor discovers this and threatens Loki, Loki journeys to Svartalfheimr and commissions the sons of Ívaldi to forge new golden hair for Sif that will grow like natural hair. The episode is recounted in Skáldskaparmál and serves as the framing narrative for the creation of the great divine treasures, including Thor’s hammer Mjölnir.

Sif appears as a named figure associated with Thor and as the mother of Ullr (by an unnamed father before her union with Thor), but has almost no independent mythological narrative. Lokasenna (st. 54) shows Sif serving Loki mead at the feast in an attempt to placate him.

The connection between Sif’s golden hair and grain is widely cited in Norse mythology scholarship. This interpretation is coherent and widely accepted in scholarship but is not explicitly stated in any primary source.