Muk (Japanese: ベトベトン Betbeton) is a Poison-type Pokémon. It evolves from Grimer starting at level 38.
Muk look very similar to its previous form, Grimer. The main differences are that Muk is larger than Grimer, and has a wider mouth and smaller eyes. It is also usually shown with its left arm being much larger than the right one, along with a strand connecting its upper and lower lip when its mouth is open. The sludge it is made of is apparently less dense than water as it has been shown to float on it in the anime.