A nomenclatural revision of fifteen taxa of Xyris (Xyridaceae) described by L.A. Nilsson (1892) is presented as part of a taxonomic revision of the genus in Brazil. All the protologues and type collections of these taxa were studied. The type collections were examined in the respective herbarium collections where they are preserved and complemented by images available on herbarium websites and from JSTOR Global Plants. Lectotypes were selected for Xyris cristata L.A.Nilsson, X. glaziowii L.A.Nilsson and X. insignis L.A.Nilsson. The holotypes, of X. glandacea L.A.Nilsson and X. stenophylla L.A.Nilsson, were discovered at the herbaria of Uppsala (UPS) and Berlin (B) respectively, and provided with their correct determinations.