A 2006 Marvel crossover written by Mark Millar with art by Steve McNiven. The seven-issue limited series centers on the Superhuman Registration Act, introduced after a battle in Stamford, Connecticut causes civilian casualties. The act requires superpowered individuals to register with the government and reveal their identities.
Iron Man leads the pro-registration faction while Captain America opposes it as a violation of civil liberties. Spider-Man, the X-Men, and other heroes choose sides as the conflict escalates. The storyline had major consequences for the Marvel Universe and was adapted for the Marvel Cinematic Universe.