Polyozellus multiplex (Thelephorales) is a species complex containing four new species.

Geographic, morphological, and internal transcribed spacer (ITS)-based molecular review of collections identified as Polyozellus multiplex revealed that it is a complex of five phylogenetic species. Average spore size-either less or more than 7 × 6 µm-splits the complex into a small-spored group of two (P. multiplex and P. atrolazulinus) and a large-spored group of three (P. mariae, P. marymargaretae, and P. purpureoniger). Basidiocarps of the small-spored species are somewhat smaller than the large-spored ones, are various shades of blue, dark all the way to black, with brownish tomentum only in early growth, have dark context, and have pilei that tend to flare out at the edge. The large-spored species produce somewhat larger sporocarps, have light or lighter context than the pileipelis, and usually retain some brown on the mature pileipellis, the edge of which tends to curl like a cabbage leaf. All will darken or blacken with age. The species of the P. multiplex complex are distributed in the northern coniferous region, with the exception of Europe. One species (P. atrolazulinus) is known from three regions, eastern Asia, western North America, and northeastern North America. Two species are known from two regions: P. purpureoniger in eastern Asia and northwestern North America and P. multiplex in eastern Asia and eastern North America. Two species have been documented in one region only: P. mariae in northeastern North America and P. marymargaretae in western North America. A combination of location, macromorphology, and spore size will usually differentiate the species of the complex.