Sif

The golden-haired wife of the god Thor.

There is not much known about her, except that she could originally have been a fertility goddess. Neither does she appear often in the myths.

The best know myth, however, is when Loki the Trickster sneaked into Sif's bedroom and lopped off her hair. Furious, Thor threatened to smash him unless Loki managed to replace the hair. He went to a great cave, the home of the sons of Ivaldi, and told them the reason of his journey. He then asked the dwarfs to spin gold as fine as Sif's hair and imbue it with magic that it will grow on her head. The dwarfs agreed and made a long wave of fine golden strands, which Loki gave to Sif.

Source: the Encyclopedia Mythica, please visit their site for much more