Aaahh!!! Real Monsters is an American animated television series developed by Klasky Csupo for Nickelodeon. It is the fifth Nicktoon after Doug, Rugrats, The Ren & Stimpy Show and Rocko's Modern Life. The show focuses on three young monsters—Oblina, Ickis, and Krumm—who attend a school for monsters under a city dump and learn how to frighten humans. Many of the episodes revolve around their zany hijinks after making it to the surface in order to perform "scares" as class assignments. The series premiered on October 29, 1994, and aired until November 16, 1997.

The episodes follow the suspenseful adventures of Ickis, Oblina, and Krumm, three young monster friends attending a monster school whose headmaster is The Gromble.

The show is set in New York City where monsters co-exist with humans, demonstrated throughout the series by the presences of the Empire State Building and the IND Subway System, and in the episode "Monster Make-Over" when Ickis refers to himself as "the ugliest, slimiest, razor fanged, sharp clawed, monster menace this side of Newark!" The dump where the monsters inhabit is implied to be Fresh Kills Landfill, but never explicitly named in the series. The monster community includes a working economic system using toenails as currency.

Aaahh!!! Real Monsters was created by Gábor Csupó and Peter Gaffney, and was the third animated series produced by Csupó's company Klasky Csupo, which also created the animated shows Rugrats and Duckman on USA Network. Before the final title was chosen, which took over five years, the series had the working titles Monsters and Real Monsters. The show was conceived after Csupó and his wife and creative partner Arlene Klasky were approached by the network Nickelodeon to create a follow-up series to Rugrats. Csupó was inspired to write a show about monsters because his own young children loved them. He also said he knew Nickelodeon would not want a series about human characters because everybody else was pitching shows about animals. Csupó drew some sketches of possible monsters on a piece of paper and successfully pitched the idea to the network: "I wanted them silly and not too skillful – and the idea worked."

Nickelodeon programming director Herb Scannell said the character design in Aaahh!!! Real Monsters was partially inspired by Yellow Submarine, a 1968 animated film that was, in turn, inspired by The Beatles. The character Gromble, in particular, bears a close resemblance to the Blue Meanie characters from that film. Director of the series Igor Kovalyov said the style was inspired by his earlier Soviet film Investigation Held by Kolobki which he and Gábor Csupó showed to the producers who then gave Kovalyov's team a lot of creative freedom with the art direction and storyboarding. Csupó said some elements of the show have a look similar to the film noir genre, and called the city dump where the monster characters reside reminiscent of the visual style from the films Blade Runner (1982) and Brazil (1985). The characters guest-star in the 1999 Rugrats episode "Ghost Story". Before that, David Eccles, the voice of Krumm, provided the monster voice coming from under Chuckie's bed.

Reviews for Aaahh!!! Real Monsters were very positive. Josef Adalian of The Washington Times praised the show's animation and sense of humor, although it was not as "hip and witty" as The Ren & Stimpy Show or The Simpsons. Although he felt the show would appeal to children over nine as well as adults, he said it may not appeal to those who "react negatively to semi-scary sights and gags about body odor, physical punishment or abusive older siblings". USA Today writer Matt Roush called it "garish and blissfully silly" and praised the show's "outrageous characters have just enough Ren & Stimpy grodiness, but tempered with exceptional sweetness". Ginny Holbert of the Chicago Sun-Times called it a "cute and clever" series with "wit and inventive creatures", and compared the animation to the work of artist Peter Max. Gannett News Service writer Mike Hughes called it a "terrific cartoon series", and said the show's "wildly perverse humor" had a "distinctly European style" that reflected Gábor Csupó's Hungarian background.

The Plain Dealer writer Tom Feran called the show "good fun" and favorably compared the series' premise to that of the animated film The Nightmare Before Christmas. Boston Herald writer Frances Katz wrote, "If there was ever a great title for a cartoon, it has to be Nickelodeon's Aaahh!!! Real Monsters'." Not all reviews were positive. The November 1994 issue of Parenting magazine listed Aaahh!!! Real Monsters as #1 in its top ten list of the worst new shows of the television season, describing it as "Graphic and scatological; it's just plain gross." Some media outlets pointed out similarities between Aaahh!!! Real Monsters and The Brothers Grunt, an MTV animated television series created by Danny Antonucci about a group of grotesque humanoid characters. Gábor Csupó rejected these comparisons and claims his show was more story- and character-driven with a different visual style, while Antonucci's show was idea-driven. Csupó did not want Aaahh!!! Real Monsters to be lumped together with The Brothers Grunt, especially since that show received low ratings and negative reviews, lasting for 8 months, and that Danny Antonucci called it "MTV's dirty little secret".

The pilot episode of Aaahh!!! Real Monsters won first prize for film animation producer for television at both the Houston Film Festival and Ottawa Film Festival. The series was nominated for a Daytime Emmy Award for Outstanding Achievement in Animation in 1995 alongside Rugrats, Animaniacs, Where on Earth Is Carmen Sandiego? and 2 Stupid Dogs. The award ultimately went to Rugrats.