Morphological and molecular features were analyzed for a species ofPhacusto better understand the phylogenetic relationships among them and establish the taxonomy. Phylogenetic analyses were based on nSSU rDNA and the research resulted in 55 new sequences. The study included species available in algal collections and those isolated directly from the environment in Poland and the Czech Republic. As a result, the obtained phylogenetic tree ofPhacusincludes 50 species, out of which 7 are represented on a tree for the first time (Phacus anacoelus, P. anomalus,P. curvicauda,P. elegans,P. lismorensis,P. minutusandP. stokesii) and many have been taxonomically verified. For all verified species, diagnostic descriptions were amended, the naming was reordered and epitypes were designated.