Superman debuts in Action Comics #1 (cover dated June 1938).

Superman is a superhero created by writer Jerry Siegel and artist Joe Shuster, first appearing in the comic book Action Comics #1, published in the United States on April 18, 1938. Superman has been regularly published in American comic books since then, and has been adapted to other media including radio serials, novels, films, television shows, theater, and video games. Superman is the archetypal superhero: he wears an outlandish costume, uses a codename, and fights evil and averts disasters with the aid of extraordinary abilities. Although there are earlier characters who arguably fit this definition, it was Superman who popularized the superhero genre and established its conventions. He was the best-selling superhero in American comic books up until the 1980s.

Action Comics #1 is the first issue of the original run of the comic book/magazine series Action Comics. It features the first appearance of several comic-book heroes—most notably the Jerry Siegel and Joe Shuster creation, Superman—and sold for 10 cents. It is widely considered to be both the beginning of the superhero genre and the most valuable comic book in the world. Action Comics ran for 904 numbered issues before it restarted its numbering in the fall of 2011. It returned to its original numbering with issue #957, published on June 8, 2016 and reached its 1,000th issue in 2018.

April 18 is the 108th day of the year in the Gregorian calendar; 257 days remain until the end of the year.