Sif is a fictional character appearing in American comic books published by Marvel Comics. The character is depicted commonly in association with the superhero Thor. Based on the Norse goddess Sif, she was created by Stan Lee and Jack Kirby and first appeared in Journey Into Mystery #102 (March 1964). As an Asgardian warrior and lover of Thor, Sif often accompanies Thor into battle. She has also battled alongside Balder, who has developed an unrequited attraction to her, as she never shows affection for anyone but Thor and certain individuals who have proved worthy to wield his hammer, Mjolnir, such as the noble alien warrior Beta Ray Bill and the mortal Eric Masterson.