Onoseris (Asteraceae, Mutisieae) is a genus of 31 species distributed from Mexico to Argentina through the Andes with its center of diversity in Peru. A phylogenetic analysis based on a detailed morphological study is provided. Urmenetea is used as the outgroup. Three most parsimonious cladograms are obtained based on the complete data set using Paup* 4.0b8. Two monophyletic groups are recognized: 1. Species with petiolate leaves, palmately veined blades with hastate base, and few-headed capitulescences, rarely thyrsoid capitulescences (O. acerifolia, O. alata, O. brasiliensis, O. cabrerae, O. castelnaeana, O. costaricensis, O. donnell-smithii, O. drakeana, O. fraterna, O. hastata, O. macbridei, O. onoseroides, O. peruviana, O. purpurea, O. sagittata, O. silvatica, and O. speciosa). 2. Species with sessile or subsessile leaves, elliptic and pinnately veined blades with attenuate base, and solitary capitula (O. albicans, O. amplexicaulis, O annua, O. chrysactinioides, O cumingii, O. gnaphalioides, O. humboldtiana, O. hyssopifolia, O. linearifolia, O. lopezii, O. minima, O. odorata, O. salicifolia, and O. weberbaueri). These monophyletic groups are recognized as subgenera Onoseris and Hipposeris respectively. Onoseris salicifolia is chosen as the lectotype of Onoseris subg. Hipposeris. Corolla polymorphism within Onoseris shows that corolla morphology alone cannot be used to distinguish between subtribes Mutisiinae and Gochnatiinae. Biogeographically, Onoseris has a continuous distribution from the Southern Andes to Northern Andes and Central America, but no individual species is distributed on both sides of the Huancabamba Zone. A group of species in subgenus Onoseris distributed in Central America and Brazil are regarded as phylogenetically derived (e.g., O. brasiliensis, O. costaricensis, O. onoseroides).