Which superhero group includes Iron Man, Thor, and the Hulk?

The superhero group that includes Iron Man, Thor, and the Hulk is the Avengers.

The Avengers are Marvel’s premier team of established heroes, often called “Earth’s Mightiest Heroes.” Unlike the X-Men, whose members are generally defined by their shared mutant identity, the Avengers bring together heroes with very different origins and abilities to face threats too large for one character to handle alone.

The team debuted in The Avengers #1, cover-dated September 1963. The original comic-book lineup consisted of Iron Man, Thor, the Hulk, Ant-Man, and the Wasp. Captain America joined in issue #4 after being discovered frozen in ice. Team membership has changed continually, with characters such as Black Panther, Hawkeye, Scarlet Witch, Vision, and Captain Marvel becoming important members.

The Fantastic Four and X-Men are also Marvel teams, while the Justice League belongs to DC Comics. The Marvel Cinematic Universe popularized a different initial lineup that included Iron Man, Captain America, Thor, Hulk, Black Widow, and Hawkeye. Even with those roster differences, the Avengers is the single canonical answer.