Sif ("In-law-relationship") is a godess in Norse mythology. Sif only appears in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda, written in the 13th century by Snorri Sturluson. In these two sources, she is known for her golden hair, as the wife of the major god Thor and, in the euhemerized prologue of the Prose Edda, as the most beautiful of women.