Sly Sludge is a recurring villain in the educational children's superhero TV series Captain Planet.

Sly Sludge is a pollutionist/con man who specialises in tricking others into thinking he and his crew are helping to build something to help the environment just so he can get free space to dump his wastes (oil, toxic sludge, and gunk).

Sly and his dumping crew do not seem to have any real reason for doing this—one would assume he is building dumps to make money, but he is never shown collecting any money, however it has been stated that "he'll pollute anything for a buck".

Sly is portrayed as a fat, lazy, greedy, money grubbing slimeball with a fondness for trickery and little care for the planet. If Sludge and his workers can not dump it in the ocean or into landspaces than they will burn it and make acid rain.

Strangely, despite being a dumper, instead of polluter clothes, he instead wears the uniform that an army soldier would, and despite being a human, his unusual last name and strange facial look makes him seem like a monster. In the series, the Planeteers must unite to summon Captain Planet to help stop men like Sludge from harming the earth.

Despite his run-ins with the superhero he continues his evil work, on some occasions he and his men load guns with oil to try and stop Captain Planet. He also appeared in the comic books based on the series.

Sly symbolizes ignorance and short term-thinking. In the two-part Captain Planet episode, Mission to Save Earth, Sly is among the five Eco Villains who create Captain Pollution. They did this by creating and using five Anti-Elemental Rings consisting of Deforestation, Toxins, Smog, Super Radiation, and Hate. Sly's element was Smog. Unfortunately for the Eco Villains, Captain Pollution was destroyed and the Anti-Elemental rings along with him, leading Sly and the other villains to flee.