Strontium Dog was a long-running British comics series starring Johnny Alpha, a mutant bounty hunter who lives in Earth's future. The series was created in 1978 by writer John Wagner (under the pseudonym T. B. Grover) and artist Carlos Ezquerra for Starlord, a short-lived weekly science fiction comic. When Starlord was cancelled, the series transferred to the British science fiction weekly 2000 AD. In 1980, Wagner was joined by co-writer Alan Grant, although scripts were normally credited to Grant alone. Grant wrote the series by himself from 1988 to 1990. Wagner revived the series after a ten-year hiatus in 2000. After Ezquerra's death in October 2018, the series was put in indefinite hiatus with no current plans for its continuation (other than some single-episode stories in special issues aimed at younger readers).

The series takes place in an imagined future after the Great Nuclear War of 2150. Due to nuclear fallout of strontium-90, humanity has an increased number of mutant births, most of whom have physical abnormalities but some of whom possess superhuman abilities. John Kreelman is born with white blank eyes and a mutant "alpha radiation" power that grants him greater perception, allowing telepathy and the ability to see through many surfaces. Facing discrimination, John Kreelman adopts the name "Johnny Alpha" and becomes a bounty hunter for the Search/Destroy Agency. Due to the origin of their mutation and their S/D badges, mutant bounty hunters are nicknamed "strontium dogs." A formidable bounty hunter, Johnny Alpha uses not only his mutant abilities in combat but also an array of high-tech gadgets and weapons.

Strontium Dog stories are often known for a bleak, minimalistic edge at times reminiscent of spaghetti westerns. Several stories veer into satire and overtly bizarre science fantasy. Johnny Alpha's adventures sometimes involve time travel (such as a mission to 1945 where he attempts to apprehend Adolf Hitler) or alternate dimension (including one that seems to be Hell). On several occasions, Johnny Alpha's time travel adventures to periods before the Great Nuclear War have featured him crossing paths with popular 2000 AD character Judge Dredd.