The American lobster, Homarus americanus, is a species of lobster found on the Atlantic coast of North America, chiefly from Labrador to New Jersey. It is also known as true lobster, northern lobster, or Maine lobster. It can reach a body length of , and a mass of over , making it not only the heaviest crustacean in the world, but also the heaviest of all living arthropod species. Its closest relative is the European lobster Homarus gammarus, which can be distinguished by its coloration and the lack of spines on the underside of the rostrum. American lobsters are usually bluish green to brown with red spines, but a number of color variations have been observed.