"Civil War" is a 2006–2007 Marvel Comics crossover storyline written by Mark Millar and penciled by Steve McNiven. The seven-issue limited series, along with numerous tie-in books, centers on a conflict that fractures the superhero community after a catastrophic incident involving the New Warriors leads to the passage of the Superhuman Registration Act. The act requires all superpowered individuals to register their identities with the government and become licensed agents, pitting those who support the legislation, led by Iron Man, against those who oppose it on civil liberties grounds, led by Captain America.
The event was one of Marvel's most commercially successful and culturally impactful storylines of the 2000s, sparking debate among fans about security versus freedom. It explored complex moral questions, with neither side presented as entirely right or wrong, and its consequences reverberated through the Marvel Universe for years, including the death of Captain America and the restructuring of the Avengers. The storyline's central ideological clash and its large-scale hero-versus-hero battles made it a landmark in modern superhero comics.