Fallout: Mile High
Super mutants are mutated humans, products of infection by the Forced Evolutionary Virus (FEV). They are much taller, bulkier and 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 two different known sources of super mutants in the post-War world – Mariposa Military Base in the Core Region (on the West Coast) and Vault 87 in the Capital Wasteland (on the East Coast). The two 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.