Fjolsvinnsmal or The Lay of Fjolsvinn is the second of two Old Norse poems which comprise the Svipdagsmál, The Lay of Svipdag. In the first poem, Svipdag enlists the aid of his dead mother, Groa, a witch, to assist him in the completion of a task set by his cruel stepmother.

At the commencement of Fjolsvinnsmal, Svipdag has arrived at a castle on a mountain top. There he encounters a giant watchman who rudely tells him to begone, Fjolsvith.

Fjolsvith is one of the names of the principal of the gods of Asgard, Odin. Fjolsvith tells him to go away, while asking him his name; Svipdag wisely conceals his name.

A game of question and answer riddles ensues, wherein Svipdag learns that Mengloth lives in the castle guarded by the Fjolsvith, and that the castle may not be entered by any save one: Svipdag. He gives his true name and the gates are opened and Mengloth greets her saviour.