Fjölvar is a being in Norse mythology, possibly a giant, with whom Odin spent time fighting and seducing women on the island of Algroen ("all green"). This episode was recounted by Odin himself in disguise while boasting of his martial skill and sexual prowess to Thor in the poem Hárbardsljód, one of the Poetic Edda written in the 13th century.
Fjölvar is an Old Norse name still used today, in the Old Norse it was used as an adjective and meant 'very wary, very cautious'.