Mr. Fantastic, also known as Reed Richards, is the leader of the Fantastic Four and the resident super-genius as well as the boyfriend (and later husband) of Susan Storm - despite his vast intelligence Reed suffers from a bit of autism and often gets himself and others in trouble with his experiments.
However he is much more responsible than Johnny Storm (aka the Human Torch) and would never harm anyone on purpose - through no true fault of his own Mr. Fantastic has become bitter enemies with the vain and power-hungry Doctor Doom, one of the few men alive who may be smarter than Reed. Of course no matter how smart Doom is he is always defeated by Reed Richards with help from his friends, the Fantastic Four.
Mr. Fantastic was created by the late Stan Lee and the late Jack Kirby.
Mr. Fantastic can bend to incredible lengths and shape his body into virtually anything, he is also virtually immune to physical injury and, of course, he is a super-genius of near immeasurable skill who can create amazing inventions at the drop of a hat to save the world or aid his allies.
Mr. Fantastic also has a very slight resistance to mind-control, being affected less than ordinary people by such attacks on his mind - whether this is a side-effect of his immense intelligence or a minor power in itself is not truly known except maybe to Mr. Fantastic himself.