Following a phenetic and phylogenetic analysis, five species of Plasmopara are recognized on Geraniaceae: P. pusilla and P. geranii-syluatici in Eurasia, P. geranii in North America, P. praetermissa sp. nov. in Eurasia and North America, and P. wilsonii sp. nov. in North America and Far East Asia. Both the D1/D2 domains of the nuLSU-rDNA and the complete ITS1-5.8S rDNA-ITS2 region were analysed with MP and Bayesian methods to reveal phylogenetic relationships of the species. All species formed highly supported monophyletic lineages, which is corroborated by their distinct morphology. A key for identification, detailed descriptions, illustrations, and data on distribution are provided.