A revision of the weedy grass genus Imperata is proposed. The present study presents the results of field and herbarium studies, supplemented by chromosome numbers, leaf anatomy, and starch gel electrophoresis. Morphological measurements were analyzed using principal component analysis and cluster analysis. Nine species are recognized including: I. cylindrica, I. condensata, I. minutiflora, I. brasiliensis, I. cheesemanii, I. tenuis, I. conferta, I. contracta, and I. brevifolia.