Kryptonite is a fictional material that appears primarily in Superman stories published by DC Comics. In its best-known form, it is a green, crystalline material originating from Superman's home world of Krypton that emits a unique, poisonous radiation that can weaken and even kill Kryptonians. Kryptonite radiation can be transmitted through any element except lead. Thus, Superman has a special lead suit to protect himself from the radiation. There are other varieties of kryptonite, such as red and gold kryptonite, which have different but still generally negative effects.

Superman is a superhero who appears in American comic books published by DC Comics. The character was created by writer Jerry Siegel and artist Joe Shuster, and debuted in the comic book Action Comics #1. Superman has been adapted to a number of other media, which includes radio serials, novels, films, television shows, theater, and video games.