Lobster, term applied to 4 groups of decapod ("10-footed") crustaceans: the coral, slipper, spiny and clawed lobsters. They comprise 163 species. The American lobster (Homarus americanus), found along the Atlantic coastline and Continental Shelf from Labrador to North Carolina, is the only species occurring in Canadian waters. It attains the greatest weight of any living arthropod: the largest male H. americanus on record weighed over 19 kg.

Lobsters are not native to the Pacific coast of Canada, but from 1896 to 1966 there were at least 11 separate introductions of American lobsters into BC waters, and even more along the US West Coast. In Canada, introductions probably totalled no more than 5000 adults. Although American lobsters seem able to survive in the Pacific, there is no evidence that any of the introductions has resulted in a reproducing population.

The clawed Homarus genus is the homard of French cuisine. The clawless spiny lobster [French langouste] is also known as crayfish.

See also Crustacean Resources.