The Justice League is a group of heroes who protect the Earth, and later the Smash World, against various threats, and serve as major protagonists in Super Smash Bros. Crossover starting with Season 37 onwards. The Justice League's founding members consist of Superman, Batman, Wonder Woman, Martian Manhunter, the Flash, Green Lantern, and Hawkgirl, although the Justice League has an expanded roster that is too big to list. Following the deaths of the Heroes of Legend's previous incarnation (twice), the Justice League have played a major role in reforming the Heroes of the World and starting Project: Utopia to maintain the peace the Heroes of Legend gave up everything for, with Batman and Superman even joining the reincarnated Heroes of Legend as their supervisors and reserve members (in Batman's case on the latter) to help the unstable Heroes of Legend regain their sanity, showing how devoted they are to helping their allies and protecting the Smash World. The Justice League have also contributed to stopping Kabuto Yakushi's invasion of the Smash World, thwarting the Revolutionaries' constant attempts to reshape the world in their image, and recently participating in the titanic clash with Bills, the God of Destruction of Universe 7, with the latter prompting Batman and Superman to extend the Justice League's ranks to everyone of their allies and becoming two of the founding members of the Justice League's sub-group, the Justice League Unlimited.
- Superman (Also a founding member of the Justice League Unlimited)
- Batman (Also a founding member of the Justice League Unlimited and a reserve Hero of Legend, part-timer)
- Wonder Woman
- Martian Manhunter
- The Flash
- Green Lantern (John Stewart)
- Batman was the first member of the Justice League to appear in Super Smash Bros. Crossover.
- The Justice League's appearance in Super Smash Bros. Crossover is based off the DCAU version of the Justice League.
- The Justice League are the first DC Comics' characters to appear in Super Smash Bros. Crossover.
- The Justice League has the same amount of founding members as their sub-group, the Justice League Unlimited, which is seven.