Description of three new taxa of Ouratea: O. paraguayensis Hassl. ex Sastre & Offroy from Paraguay and Bolivia, distinct of O. superba Engl. which occurs in Amazonian Basin and the Guyanas, by its smaller flowers and the leaf margins serrate, not serrulate; O. paraguayensis f. boliviensis Sastre & Offroy with inflorescences larger than in the forma paraguayensis, and with conical buds, not obovoid, with many specimens intermediate between both forms; O. pastazana Sastre & Offroy, endemic from Pastaza Province in Ecuador, with flowers of the same size as those of O. paraguayensis, but with the leaf margins serrulate as in O. superba. Comparisons are made with two other Venezuelan vicariant species also with small flowers, O. marahuacensis Maguire & Steyerm. (Amazonas state) and O. apurensis Sastre (Apure state). The peri-Amazonian distribution of the species with small flowers, suggests an old area of the ancestral species of which populations became isolated during dry Quaternary periods, each isolated population giving, by genetic drift, endemo-vicariant species. Both O. paraguayensis formas suggest the presence of a cline, perhaps responsible, actually, for a specific sympatric differentiation. Ouratea superba and some synonymous taxa are lectotypified.