What a Cartoon! (later known as The What a Cartoon! Show and The Cartoon Cartoon Show) is an American animated anthology series created by Fred Seibert for Cartoon Network. The shorts were produced by Hanna-Barbera Productions; by the end of the run, a Cartoon Network Studios production tag was added to some shorts to signal they were original to the network. The project consisted of 48 cartoons, intended to return creative power to animators and artists, by recreating the atmospheres that spawned the iconic cartoon characters of the mid-20th century. Each of the shorts mirrored the structure of a theatrical cartoon, with each film being based on an original storyboard drawn and written by its artist or creator. Three of the cartoons were paired together into a half-hour episode.

What a Cartoon! premiered under the World Premiere Toons title on February 20, 1995. The premiere aired alongside a special episode of Cartoon Network's Space Ghost Coast to Coast called "World Premiere Toon-In", which features interviews with animators Craig McCracken, Pat Ventura, Van Partible, Eugene Mattos, and Genndy Tartakovsky, as well as model Dian Parkinson. During the original run of the shorts, the series was retitled to The What a Cartoon! Show and later to The Cartoon Cartoon Show until the final shorts aired on August 23, 2002.

The series is influential for helping to revive television animation in the 1990s and serving as a launching point for the Cartoon Network animated television series Dexter's Laboratory, Johnny Bravo, Courage the Cowardly Dog, Cow and Chicken, I Am Weasel, and The Powerpuff Girls. Once it had several original shorts, those became the first Cartoon Cartoons. Following Fred Seibert's departure in 1997, Sam Register took control of the show in 1998, and by 2000, rebranded it into The Cartoon Cartoon Show, with more Cartoon Network originals being spawned from the showcase, including Sheep in the Big City, Grim & Evil (consisting of The Grim Adventures of Billy & Mandy and Evil Con Carne), Whatever Happened to... Robot Jones?, Codename: Kids Next Door, and Megas XLR. From 2005 to 2008, The Cartoon Cartoon Show was revived as a block for reruns of older Cartoon Cartoons that had been phased out by the network.