Sixty-five species of American coral snakes (genus Micrurus) range from the southern United States to Argentina. Only two species live in the United States. The eastern coral snake, or harlequin snake (M. fulvius), is about a metre (3.3 feet) long and has wide red and black rings separated by narrow rings of yellow. The Arizona coral snake (Micruroides euryxanthus) is a small (40–50-cm) inhabitant of the American Southwest. The rhyme “Red on yellow, kill a fellow, red on black, venom lack” distinguishes coral snakes from similar North American snakes. There are 50 genera of coral snake mimics such as false coral snakes (see king snake and scarlet snake), and nearly one-third of all American species have some coral snake pattern.

Most coral snakes prey on other snakes, particularly worm snakes and blind snakes, with lizards being a secondary food source. New World coral snakes lay from 1 to 13 eggs. The longevity record for Micrurus in captivity is 18 years.

Coral snakes belong to the family Elapidae (elapid), which also includes cobras and various other venomous snakes. Old World coral snakes include eight species of Calliophis and five species of Sinomicrurus in Asia, plus the single Hemibungarus species of the Philippines. In the two East Indian (East Indies) species of Maticora, the venom glands extend more than one-third of the way down the body. Two African coral snakes (Homoroselaps) are orange, black, and yellow.