Goomboss (aka King Goomba, and Goomba King), whose name is a portmanteau of "Goomba" and "boss", is a stage boss in the video game Super Mario 64 DS. As the king of the Goombas, Goomboss is roughly ten times the height of a regular Goomba. In fact, He may even be the Goomba King from Paper Mario!

Goomboss holds a particular vengeance on Mario for having stomped on his brethren for years. (Goombas have starred in every major Mario game release since Super Mario Bros.) He locks Mario up, and it is left for Yoshi to defeat him for the key to unlock Mario.

The Goomboss Battle stage, accessible through the portrait of Mario behind the Rec Room, is set in a decaying forest with rising and falling tree stumps surrounded by toxic gas. The edges of the small course are lined with " " pitfalls, making it quite difficult for a beginner's level (without unlocking Mario, the player cannot advance to fight Bowser for the first time). The course holds two Power Stars -- a red coin star and a switch star.

Goomboss can be defeated by all four characters in the game; however, the player needs to defeat him as Yoshi in order to unlock the remaining ones. Goomboss attacks by generating regular-sized Goombas behind him and trotting rapidly in a circular fashion. Yoshi can create eggs out of Goombas and fling them at the Goomboss, while the other three characters, having no egg-creation ability, must instead punch the Goombas into him. After three hits, the Goomboss finally explodes in a shower of Goombas and provides the key to Mario's room in the character-change area.

On an interesting note, Goomboss' introduction and losing words are unique for each of the four characters. The same applies to the Big Boo and Chief Chilly.