The Grim Adventures of Billy & Mandy (also known as Billy & Mandy) is an American animated television series created by Maxwell Atoms for Cartoon Network, and is the 14th of the network's Cartoon Cartoons (albeit namely when it was part of Grim & Evil; the show is considered separate from Cartoon Cartoons otherwise). It follows two children named Billy — a slow-witted boy — and Mandy — the cynical best friend — who, after winning a limbo game to save Billy's pet hamster, gain the mighty Grim Reaper as their best friend in eternal servitude and slavery.

Billy & Mandy was a spin-off of Grim & Evil, along with Evil Con Carne. The show ran from June 13, 2003 to November 11, 2007, but a spin-off film titled Underfist: Halloween Bash aired on October 12, 2008. In addition to the episodes, three movies, two special episodes, and nineteen shorts were made, with 3 award wins for the series as a whole. Billy & Mandy has also been made into a video game as well as various licensed merchandise. Reruns of the show have occasionally aired on Boomerang.