Ambush Bug is a superhero appearing in American comic books published by DC Comics. His real name is supposedly Irwin Schwab, but he has mental problems that prevent him from truly understanding reality around him, so even his true identity might be no more than a delusion on his part. His origin is disputed, although the most commonly accepted origin is that Brum-El (an allusion to Beau Brummell as well as Superman's father Jor-El) of the planet Schwab sent his clothes from his supposedly doomed planet, hoping that his wardrobe would survive, only to have it intercepted by a giant radioactive space spider. In the resulting crash, only two articles of clothing survived: the Ambush Bug suit, which was subsequently found by Irwin Schwab; and "Argh!Yle!", an argyle sock with a Doctor Doom–like complex, complete with metal mask.

Created by artist Keith Giffen as an intentionally silly character, Ambush Bug first appeared in DC Comics Presents #52 (Dec. 1982) and would make appearances in several other Superman-related comic books in the early 1980s. Paul Kupperberg, who wrote Ambush Bug's first story, recalled, "as Keith was in the office, he sat in on the plotting and offered up Ambush Bug as an antagonist. The Bug is entirely Keith's creation ..." Giffen stated that both Ambush Bug and Lobo were derived from Lunatik, a character he created in high school. Giffen said that his original pitch was "Bugs Bunny as a super-villain".

In response to positive reader reaction to the character's first appearance, editor Julius Schwartz directed Giffen to create another Ambush Bug story for DC Comics Presents #59. At first, Ambush Bug was a villain, named after a type of insect, and having a green, skintight suit with two orange antennae containing miniature robot bugs that enable him to teleport. After attacking Superman and other heroes, Ambush Bug decides instead to be a superhero as well. He also fancies himself Superman's friend, which only annoys the hero even more than his early villainy. The costume becomes permanently affixed to his body, and he gains the power to teleport by himself. While trying to fix one of the miniature bugs, it explodes, causing a chain reaction and a blast that destroys all of the bugs and tints Ambush Bug's costume temporarily black; he then becomes capable of teleporting even without the bugs (briefly considering changing his moniker to Black Beetle instead).

Ambush Bug became popular enough to be featured in two comic book miniseries and several specials, plotted and pencilled by Keith Giffen and scripted by Robert Loren Fleming. The series contains many comic book-enthusiast and DC in-jokes and satire; series editor Julius Schwartz is also a character in the book.

During his own four-part series in 1985, he picks up a doll and, thinking it is alive, "adopted" it as a partner called "Cheeks, The Toy Wonder", complete with its own costume.

In 2001, Ambush Bug appears as a member of the "Justice League of Anarchy" alongside Plastic Man, the Creeper, Harley Quinn, 'Mazing Man, and the Trickster. This group of DC Universe troublemakers made a one-panel cameo in a series exploring variations on the JLA acronym, JLA: Justice League of Amazons.

Ambush Bug is largely considered an absurd character and is rarely used by other writers, though he still exists in the DC Universe and occasionally still appears in some DC Comics. His popularity amongst creators has led to many "cameos", sometimes with as little as his antennae being visible. In the 2006 series 52, Ambush Bug appears as part of Firestorm's short-lived Justice League of America. In Countdown to Final Crisis (2007), Jimmy Olsen briefly gains the appearance of Ambush Bug and subconsciously uses his power of "Dumb Luck" to locate Forager.

An Ambush Bug miniseries, Ambush Bug: Year None, debuted in 2008, plotted and pencilled by Giffen, and written by Fleming, with Jann Jones serving as editor. The final issue was published almost a year after the rest of the series. Dan DiDio claims to have lost issue #6, which was skipped to finish off the series with issue #7.