According to Snorri Sturluson, one of the Ásynjur. She is attested in Gylfaginning:
The seventh is Sjöfn: she is most diligent in turning the thoughts of men to love, both of women and of men; and from her name love-longing is called sjafni.
Sjöfn is presumably another name for Frigg.
- Gylfaginning, 35.