Groo the Wanderer is a fantasy/comedy comic book series written and drawn by Sergio Aragonés, rewritten, co-plotted and edited by Mark Evanier, lettered by Stan Sakai and colored by Tom Luth. Over the years it has been published by Pacific Comics, Eclipse Comics (one special issue), Marvel Comics (under its Epic imprint), Image Comics and Dark Horse Comics.

Groo was one of the first widely successful creator-owned comics, one of the few successful humorous comic books in the United States (outside Archie Comics) during its time, and one of the longest-running collaborations in comic book history. In 2011 IGN ranked Groo 100th in the "Top 100 comic books heroes".

Groo (the epithet "the Wanderer" is informal and rarely mentioned within the stories) first appeared as a parody of the brutal sword and sorcery heroes who were popular at the time of his creation in the 1970s, especially Conan the Barbarian as presented in Marvel Comics. Groo is a large-nosed buffoon of unsurpassed stupidity who constantly misunderstands his surroundings. Possessed of superlative skills in swordsmanship (the only task at which he is remotely competent), he delights in combat but otherwise is a peaceable and honest fellow who tries to make his way through life as a mercenary or by working odd jobs. He is incredibly accident-prone, and despite generally good intentions causes mass destruction wherever he goes. Most of his adventures end with him either oblivious to the mayhem he has wrought or fleeing an angry mob. His penchant for destruction has become so widely known that just the news of Groo approaching is sometimes enough to cause chaos among the population. Groo occasionally meets with respect and good fortune, but it does not last. Businesses, towns, civilizations, and cultures have all been unwittingly destroyed by Groo. Such is Groo's incompetence that so much as his stepping onto a ship can cause it to sink.

Groo has slain entire armies with nothing more than his swords, which appear to be a pair of katanas. Groo loves these frays, as he calls them, and often charges into the melee with a cry of "Now Groo does what Groo does best!" He is indiscriminate in the use of his battle skills, usually leaping into the bloodshed before attempting to ascertain the reasons for the fight, or even who is on what side. Even when Groo does join battle intending to fight for a particular side, he is prone to forget which side he is on or be tricked into fighting his unfortunate allies, often causing him to utter "Did I err?" in confusion once everybody is dead.