|First appearance||Volcanic Percolator Day Spa|
|Abilities||Contains 18 Small Ugly Goo which withstand spikes|
Ugly Goo is a species of Goo in the video game World of Goo. They are first introduced in the level Volcanic Percolator Day Spa, and have the extra ability to be broken down into 18 Small Ugly Goo that are often used for their durability.
The Ugly Goo has a sister Goo named Beauty Goo which in contrast is pink in color and supposedly much prettier than the Ugly Goos, which, the game implies heavily, should be used for sacrificial acts to help Beauty Goo, as referenced in Genetic Sorting Machine.
The sole purpose of Ugly Goo is to be broken down into Small Ugly Goo. Since Small Ugly Goo cannot be collected in either the pipe or red pipe (except in Volcanic Percolator Day Spa), they are most commonly used to aid the Beauty Goo in getting to the latter pipe. As the Small Beauty Goo will pop on contact with spikes and other hazardous surfaces while the Small Ugly Goo will not; their purpose served is much more barbaric. In Genetic Sorting Machine, three Ugly Goo must be murdered to fill a dangerous, spiked pit that the Beauty Goo cannot cross. Ugly Goos cannot be used to build structures nor picked up by the pointer.
- In Product Launcher, there are three giant dark black Goo Balls that are slightly smaller than the Ugly Goo, but have the same general effect, only different in that the balls released are flammable and explosive.
- The eyes of Small Ugly Goo and Small Beauty Goo are indistinguishable from each other and as such, both can be collected by pipes.