A new species of Leporinus in the L. cylindriformis group is described from the Río Orinoco basin, Venezuela. This new species can be separated from congeners by the combination of an extremely dorsoventrally slender body, the presence of a prominent midlateral spot positioned ventral to the dorsal fin, and the absence of any other intense dark pigmentation. The new species is most similar to L. aripuanaensis from the Rio Aripuanã, Brazil, but can be most easily differentiated from that species by the absence (79% of specimens) or faint presence (21% of specimens) of a circular dark spot over the hypural plate in the new species, versus the presence of an intensely pigmented dark spot in that position, respectively. It can be further distinguished from L. aripuanaensis by the modal number of predorsal scales (12 versus 11). Small juveniles of the two species do not differ morphometrically, but their allometric growth trajectories differ. Above 70 mm SL, the new species differs from L. aripuanaensis in interorbital width (34–44% HL versus 30–34%) and eye diameter (29–34% HL versus 26–30% HL). This new species represents the most recent of a long series of newly discovered taxa within Leporinus and reinforces the Orinoco Basin as a region of high endemism.