King Krypton is the name bestowed by Jimmy Olsen on a "giant gorilla"—a mighty "super-gorilla" from the planet Krypton, endowed with super-powers identical to Superman's --which Superman and Jimmy Olsen encounter in an African jungle in March 1958.
Theorizing that the so-called Gorilla of Steel is probably a Kryptonian experimental monkey launched into outer space prior to the death of Krypton, Superman engages in a series of fearsome, albeit indecisive, battles with the "super-simian," determined to prevent it from reaching civilization and wreaking untold havoc there.
Ultimately, however, under the influence of a Kryptonite meteor's baleful green rays, King Krypton undergoes an "uncanny transformation" from super-gorilla into human being and, with his dying breaths, explains that he is in reality a scientist from Krypton who was accidentally transformed into a gorilla by the tragic malfunctioning of an experimental "evolution accelerator" and then launched by his assistant into orbit around Krypton in the hope that the "powerful cosmic rays" of space would ultimately restore him to his human form. Now, ironically, the Kryptonite meteor has succeeded in freeing the Kryptonian from his gorilla prison, but only at the cost of snuffing out his life, since all Kryptonian survivors are fatally vulnerable to Kryptonite (Act No. 238: "The Super-Gorilla from Krypton").