Sphere of influence: Relationships
Famous portraits: None contemporary
The name Sif means "in-law-relationship" and in all probability her function as a goddess could be found in that name - though it is not entirely clear, she is not that frequent in the Nordic sagas.
The goddess Sif is the wife of the thunder-god Thor in Norse Mythology. With him she has the daughter Thrud (Þrúðr - meaning "strength" and "woman") and from some previous relationship she has the son Ullr ("glory"). The father of that child is unknown, and Thor is referred to as being a step-father - that is all we know on that subject.
Sif is mentioned in both the Poetic Edda (written in the 13th century - but based on elder sources) and the Prose Edda (written in the 13th century by Snorre Sturluson).
Sif's hair is golden - the god Loki cuts it off once when the goddess was sleeping, but he is caught (and threatened) by her husband Thor, and Loki promises to replace her hair, and commissions a net of pure gold to be made for her head. When she put it on it the golden hair got stuck to her head - and replaced her own hair so that she actually had hair made of pure gold.
The talk of her golden hair, and the golden hair being cut, has made some scholars talk about Sif being some kind of fertility goddess - and her hair being a symbol for the growing fields, cut down when ripe. But this is a rather modern theory that has little to do with actual evidence from ancient sources.
The portrait here of Sif is made by Jenny Nyström.