Wied's marmoset, also known as Wied's black-tufted-ear marmoset, is a New World monkey that lives in tropical and subtropical forests of eastern Brazil. Unlike other marmosets, Wied's marmoset lives in groups consisting of 4 or 5 females and 2 or 3 males. They are matriarchal, and only the dominant female is allowed to mate. Like other marmosets, the offspring are always born in pairs.

The marmosets, also known as zaris or sagoin, are twenty-two New World monkey species of the genera Callithrix, Cebuella, Callibella, and Mico. All four genera are part of the biological family Callitrichidae. The term "marmoset" is also used in reference to Goeldi's marmoset, Callimico goeldii, which is closely related.