Any one of numerous species of small South American monkeys of the genera Hapale and Midas, family Hapalidæ. They have long soft fur, and a hairy, nonprehensile tail. They are often kept as pets. Called also squirrel monkey.
The marmosets are the genus Callithrix of New World monkeys. One species not classified in this genus also has common names including the word "marmoset", the Goeldi's Marmoset (Callimico goeldii). This article is only about the 18 Callithrix species.