Loki Laufeyson is a character appearing in American comic books published by Marvel Comics. The character was created by writer Stan Lee, scripter Larry Lieber and penciller Jack Kirby, and is based on the Norse mythological deity of the same name. Although a version of Loki first appeared in Venus #6 (August 1949), his characterization as the adoptive brother and nemesis of the superhero Thor, which has persisted to the modern age, was only introduced in Journey into Mystery #85 (October 1962).

In his comic book appearances, Loki is depicted as the Asgardian God of Mischief, a cunning trickster, and a master of Asgardian magic and sorcery. After learning of his true origin as a Frost Giant from Jotunheim, Loki grows jealous of Thor and frequently plots to take the throne of Asgard for himself. His schemes of conquest ultimately reach Earth and inadvertently lead to the formation of the Avengers. While usually portrayed as a supervillain, Loki has also been an antihero at times, working with heroes if their goals align and if it benefits him.

Loki has appeared in several ongoing series, limited series and alternate reality series, including the 4-issue series Loki in 2004 and 2006, being the main character of Journey into Mystery from issues 622 to 645, appearing in new issues of Young Avengers in 2013 and receiving four more solo series, Loki: Agent of Asgard in 2013, Vote Loki in 2016, Loki in 2019 and Loki in 2023. The character has been adapted in various media incarnations, having most notably been portrayed by Tom Hiddleston in the Marvel Cinematic Universe (MCU) media franchise.