Mister Fantastic is a Marvel Comics superhero who is the leader of the Fantastic Four. He has the ability to manipulate his body by stretching and shaping it to any shape he desires. The Fantastic Four established the conceit of the characters having been adapted to comic books within the context of the Marvel Universe, with the Fantastic Four having sold Marvel a license to use their likenesses

Several alternate versions of Mr. Fantastic have been encountered by the Fantastic Four. The Counter-Earth version of Reed Richards was exposed to cosmic rays that gave him the ability to transform into a purple-skinned behemoth called the Brute. The Brute made his way to Earth, where he trapped Mr. Fantastic in the Negative Zone and replaced him. He managed to trap the Human Torch and the Thing shortly thereafter, but was found out by the Invisible Woman, who rescued her teammates and left the Brute trapped in their place.

Although the Fantastic Four have numerous devices, crafts, and weapons, this is what Reed carries on him at all times: Fantastiflare: Launches a fiery “4” into the sky that is used during combat situations to let other members of the group know their location.

Like all the Fantastic Four costumes and the rest of Reed’s wardrobe, his suit is made of “unstable molecules”. This means that the suit is attuned to his powers, which is why Johnny’s costume doesn’t burn when he “flames on”, Sue’s costume turns invisible when she does, and Reed’s costume stretches with him. The costume also insulates them from electrical assaults. In addition, the team's uniforms are also, in essence, wearable computers.

Richards, who took the name Mister Fantastic, was now able to stretch his body into nearly any shape he could imagine (similar to the earlier Plastic Man). His fiancée, Susan Storm, gained the ability to become invisible at will and named herself the Invisible Girl (later the Invisible Woman). She later developed the ability to project force fields, create invisible objects, and turn other objects visible or invisible. Her younger brother, Johnny Storm, possessed the incendiary powers of the Human Torch, enabling him to control fire, project burning bolts of flame from his body, and fly. Finally, pilot Ben Grimm was transformed into a craggy, orange-skinned monster with incredible strength and a nearly invulnerable hide. Filled with self loathing and self pity, he dubbed himself the Thing.