Super Mutant (Fallout)

"Ah crud! You know what's worse than those ghouls, raiders, deathclaws and the Enclave?! Super mutants!? Who the heck are these bastards? Well, I know they're immune to disease and radiation, very muscular, taller and bulkier enough to attract the ladies, have some superhuman strength and endurance, and despite being so damn sterile, have rapid regeneration of their cells to make them virtually and/or biologically immortal while not immune to death from injury, but that's EVEN way more worse than those factors; they're even so unintelligent. They're just stupid. Well, that's just great."

--Su Ji-Hoon, A Brave New World

Super mutants are mutated humans, products of infection by the Forced Evolutionary Virus (FEV). They are much taller, bulkier and more muscular than pure strain humans, have (mostly) green, gray, or yellowish skin, are immune to disease and radiation, and are gifted with superhuman strength and endurance. Although they are completely sterile, the rapid regeneration of their cells caused by FEV makes them virtually biologically immortal (but not immune to death from injury).

There are four different known sources of super mutants in the post-War world - Mariposa Military Base in New California (on the West Coast), Vault 87 in the Capital Wasteland (on the East Coast), the FEV labs of the Institute in the Commonwealth (East Coast), and Huntersville in Appalachia (East Coast). The four populations have separate histories and origins, and are yet to interact with each other. While originally the term was only used to refer to the Mariposa stock, the Brotherhood of Steel carried the term with them and applied it to those from Vault 87 upon encountering them.