Possibly the name of female jötunn. She is solely attested in the eddic poem Fjölsvinnsmál, where she is mentioned as the keeper of the legendary weapon Lævateinn. The weapon will be given only to the one who will bring a rare object to the "goddess of gold." When Svipdagr inquires what that object that might be, Fjölsviðr replies that he must carry the bright sickle (i.e., tail feather) that lies in Víðópnir's wings in a bag to Sinmara. This creates an unsurmountable paradox, as the tail feather can not be obtained without the weapon.
- Fjölsvinnsmál, 27-31.