"Fear Itself" is a 2011 crossover comic book storyline published by Marvel Comics, consisting of a seven-issue, eponymous miniseries written by Matt Fraction and illustrated by Stuart Immonen, Wade Von Grawbadger, and Laura Martin, a prologue book by writer Ed Brubaker and artist Scot Eaton, and numerous tie-in books, including most of the X-Men family of books.

"Fear Itself" was first announced by then-Marvel Editor-in-Chief Joe Quesada, Executive Editor Tom Brevoort and X-Men group editor Axel Alonso at a press conference held at Midtown Comics Times Square on December 21, 2010. The story, whose title is a reference to the famous quote by Franklin D. Roosevelt, "The only thing we have to fear is fear itself", depicts the various superheroes of the Marvel Universe contending with the Serpent, an Asgardian fear deity who causes global panic on Earth, and who seeks to reclaim the throne of Asgard he contends was usurped by his brother, Odin, father to Thor, when the latter vanquished him ages ago. Within the comics, the characters refer to this conflict as The Serpent's War. Although it is a company-wide crossover, it emphasizes Captain America and Thor, as with past crossovers of the late 2000s.