Mark Grayson is teenage superhero Invincible. He was a normal high school senior with a normal part-time job and otherwise normal life, except his father Nolan is the superhero Omni-Man, the most powerful superhero on the planet. At the age of 17, Mark begins to display superpowers, which come from his father being a member of the Viltrumite race, who, according to Nolan, pioneer the galaxy on a mission of benevolence and enlightenment.

As Invincible, Mark begins working as a superhero, with his father acting as his mentor, and meeting other heroes (including Robot, Rex Splode, Dupli-Kate and Atom Eve), discovering that his Physics teacher has been turning his students into human bombs, to foiling a plan by the Mauler Twins to make an army of robots. Meanwhile Omni-Man is kidnapped by aliens, taken to another dimension, but returns after what seems to be only a few days, but was actually eight months to him.