|- valign=top |Kingdom:||Protista |- valign=top |Division:||Heterokontophyta |- valign=top |Class:||Phaeophyceae |- valign=top |Order:||Laminariales |} |} Kelp are large seaweeds, belonging to the brown algae and classified in the order Laminariales. There are about 30 different genera; sometimes members of the order Fucales are also considered kelp. Kelp grows in underwater forests (kelp forests) in clear, shallow, oceans, requiring nutrient rich water below about 20°C. It is known for its high growth rate - the genus Macrocystis grows up to 30 cm per day, to a total length of up to 60 metres.
- bull-head kelp (Nereocystis luetkeana), a northwestern American species. Used by coastal Native Americans to create fishing nets.
- giant kelp (Macrocystis pyrifera), the largest seaweed. Found in the Pacific coast of North America.
- konbu (Laminaria japonica), an edible specie of kelp found in Japan.
Kelp ash is calcined and rich in iodine and alkali. In great amount, kelp ash can be used in soap and glass production. Alginate, a kelp-derived carbohydrate, is used to thicken products like ice cream, jelly, and toothpaste, as well as in manufactured goods.
Some animals are named after the kelp, either because they inhabit the same habitat as kelp or because they feed on kelp.
- Kelp crab (Pugettia producta), the Pacific coast of North America.
- Kelpfish (blenny) (e.g., Heterosticbus rostratus, genus Gibbonsia), the Pacific coast of North America.
- Kelp Goose (kelp hen) (Ocydromus fuscus), New Zealander
- kelp pigeon (sheathbill) (Chionis sp), Antarctic
- Kelp forest
- bladder wrack
- Kelp Records
- KeLP Programming System
- Monterey Bay Aquarium, which displays a kelp forest and its wildlife.