The “black,” or black-mouthed, mamba (Dendroaspis polylepis), averaging 2–2.5 metres (6.6–8.2 feet) in length (maximum 3.5 metres), ranges in colour from gray to dark brown but is never actually black. Its name derives from the inside of the mouth, which is black, in contrast to the white mouths of green mambas and other snakes. The black mamba inhabits rocky savanna and can often be encountered on the ground, where it seems to be fond of termite mounds. Six to 20 eggs are laid in termite mounds or tree hollows. Prey consists primarily of small mammals and birds.

The black mamba is one of Africa's most dangerous snakes, owing to its large size, quickness, and extremely potent venom. It has an aggressive reputation, though unprovoked attacks on humans have not been proved. The snake will, however, defend itself if threatened or molested. It has a nervous disposition, and if disturbed it may rear up and threaten with an open mouth and slightly expanded or flattened neck (or hood) before striking. Even though most bites are fatal, it is responsible for only a small number of deaths annually. In captivity, black mambas have lived more than 20 years.

The three green mamba species are smaller (1.5–2 metres, maximum 2.7 metres) and are usually found in trees. The East African green mamba (D. angusticeps) of East and South Africa, Jameson's mamba (D. jamesoni) of Central Africa, and the West African green mamba (D. viridis) are all more timid than the black mamba and have not been reported to attack humans. Like the black mamba, they will flatten their necks into a narrow hood as a defensive posture. Green mambas prey upon birds, small mammals, and lizards and lay from 5 to 17 eggs. Two of the three green mambas have record longevities of more than 18 years in captivity. Mambas are members of the cobra family (Elapidae (elapid)).