Her hair was of pure gold – and this hair set off one of the most consequential stories in all of mythology. Sif, wife of the thunder god Thor, seems at first glance a quiet goddess. Yet her golden hair binds together the sky, the dwarves’ forge and the cornfields of the earth.
Sif (Old Norse Sif, ‘kinship, clan, bond’) is one of the Æsir and Thor’s wife. Snorri stresses one thing above all: her beautiful, long hair of gold. It is precisely this hair that makes her a key figure – not through deeds of her own, but through what a wicked prank sets in motion.
Out of sheer malice, Loki cuts off the golden hair of the sleeping Sif. When Thor discovers this, his fury is so great that Loki fears for his life and must find a replacement. He goes to the dwarves, the sons of Ívaldi, and has new, real gold hair forged that grows like natural hair the moment it touches Sif’s head.
But it does not stop there: in the same course further wonders are made, and from Loki’s reckless wager with the dwarves Brokkr and Sindri are finally born the greatest treasures of the gods – among them Odin’s spear Gungnir, the ring Draupnir and Thor’s hammer Mjöllnir itself. Thus Sif’s shorn hair stands at the beginning of the entire treasure-lore of the North.
Why golden hair of all things? Many scholars read Sif as an earth and fertility goddess: her flowing gold hair is an old image for the ripe, golden-yellow cornfields of late summer. That it is Loki of all figures – often a shape of chaos and fire – who ‘mows off’ her hair, and that it grows back, fits the cycle of harvest and return. At Sif’s side stands Thor, the god whose thunder-rain makes the fields grow in the first place. A fitting pair: thunder and harvest.
“Her hair was of gold,
finely spun and grown alive.”
— image after Snorri’s Skáldskaparmál (sense following Simrock, public domain)

Thor (Donar) · The Treasures of the Gods · Mjöllnir · Loki · Frigg.
Poetic Edda: Lokasenna, Hárbarðsljóð. Snorri Sturluson, Prose Edda (Skáldskaparmál: Sif’s hair and the treasures; Gylfaginning), c. 1220. German public-domain translation: Karl Simrock, Die Edda (1851). Scholarship: Rudolf Simek, Dictionary of Northern Mythology; John Lindow, Norse Mythology (2001).