The black-tufted marmoset (Callithrix penicillata) is a species of New World monkey that lives primarily in the Neotropical gallery forests of the Brazilian Central Plateau.

It ranges from Bahia to Paraná,[3] and as far inland as Goiás, between 14°S and 25°S, and can commonly be seen in the Rio de Janeiro city where it was introduced.

The black-tufted marmoset diet consists primarily of tree sap, which it obtains by nibbling the bark with its long lower incisors.

Large birds of prey are the greatest threat to the black-tufted marmoset, however, snakes and wild cats also pose a danger to them.

The offspring are extremely dependent on their parents and though they are sexually mature at 18 months, they typically do not mate until much later, staying with their family group until they do.

In Rio de Janeiro State, where it was introduced alongside the common marmoset, it is considered as an invasive species posing a danger to the survival of the endangered golden lion tamarin through competition.

Management of the species in its invaded habitat has included proposals for sterilization of reproductive-age individuals, relocation, and public awareness campaign for prevention of further releases.