The Santarem marmoset, also known as the black and white tassel-ear marmoset, is a marmoset endemic to the Brazilian states of Amazonas and Pará.

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.