﻿AbstractMazamanemorivaga(Cuvier, 1817) is a gray brocket deer that inhabits the Amazon region. An assessment of previous studies revealed inconsistencies in its current taxonomic classification, suggesting the need for an update in its genus classification. A taxonomic repositioning of this species is proposed through the collection of a specimen from its type locality (French Guiana) with subsequent morphological (coloring pattern, body measurements, and craniometry), cytogenetics (G Band, C Band, conventional Giemsa, Ag-NOR staining, andBACprobe mapping), and molecular phylogenetic analysis (mitochondrial genesCyt Bof 920 bp,COI Iof 658 bp, D-loop 610 bp), and comparisons with other specimens of the same taxon, as well as other Neotropical deer species. The morphological and cytogenetic differences between this and other NeotropicalCervidaeconfirm the taxon as a unique and valid species. The phylogenetic analysis evidenced the basal position of theM.nemorivagaspecimens within theBlastocerinaclade. This shows early diversification and wide divergence from the other species, suggesting that the taxon should be transferred to a different genus. A taxonomic update of the genus name is proposed through the validation ofPassalitesGloger, 1841, withPassalitesnemorivagus(Cuvier, 1817) as the type species. Future research should focus on evaluating the potential existence of other species within the genusPassalites, as suggested in the literature.