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The genus <i>Thielavia</i> is morphologically defined by having non-ostiolate ascomata with a thin peridium composed of <i>textura epidermoidea</i>, and smooth, single-celled, pigmented ascospores with one germ pore. <i>Thielavia</i> is typified with <i>Th. basicola</i> that grows in close association with a hyphomycete which was traditionally identified as <i>Thielaviopsis basicola</i>. Besides <i>Th. basicola</i> exhibiting the mycoparasitic nature, the majority of the described <i>Thielavia</i> species are from soil, and some have economic and ecological importance. Unfortunately, no living type material of <i>Th. basicola</i> exists, hindering a proper understanding of the classification of <i>Thielavia</i>. Therefore, <i>Thielavia basicola</i> was neotypified by material of a mycoparasite presenting the same ecology and morphology as described in the original description. We subsequently performed a multi-gene phylogenetic analyses (<i>rpb2</i>, <i>tub2</i>, ITS and LSU) to resolve the phylogenetic relationships of the species currently recognised in <i>Thielavia</i>. Our results demonstrate that <i>Thielavia</i> is highly polyphyletic, being related to three family-level lineages in two orders. The redefined genus <i>Thielavia</i> is restricted to its type species, <i>Th. basicola</i>, which belongs to the <i>Ceratostomataceae</i> (<i>Melanosporales</i>) and its host is demonstrated to be <i>Berkeleyomyces rouxiae</i>, one of the two species in the "<i>Thielaviopsis basicola</i>" species complex. The new family <i>Podosporaceae</i> is sister to the <i>Chaetomiaceae</i> in the <i>Sordariales</i> and accommodates the re-defined genera <i>Podospora</i>, <i>Trangularia</i> and <i>Cladorrhinum</i>, with the last genus including two former <i>Thielavia</i> species (<i>Th. hyalocarpa</i> and <i>Th. intermedia</i>). This family also includes the genetic model species <i>Podospora anserina</i>, which was combined in <i>Triangularia</i> (as <i>Triangularia anserina</i>). The remaining <i>Thielavia</i> species fall in ten unrelated clades in the <i>Chaetomiaceae</i>, leading to the proposal of nine new genera (<i>Carteria</i>, <i>Chrysanthotrichum</i>, <i>Condenascus</i>, <i>Hyalosphaerella</i>, <i>Microthielavia</i>, <i>Parathielavia</i>, <i>Pseudothielavia</i>, <i>Stolonocarpus</i> and <i>Thermothielavioides</i>). The genus <i>Canariomyces</i> is transferred from <i>Microascaceae</i> (<i>Microascales</i>) to <i>Chaetomiaceae</i> based on its type species <i>Can. notabilis</i>. <i>Canariomyces</i> is closely related to the human-pathogenic genus <i>Madurella</i>, and includes three thielavia-like species and one novel species. Three monotypic genera with a chaetomium-like morph (<i>Brachychaeta, Chrysocorona</i> and <i>Floropilus</i>) are introduced to better resolve the <i>Chaetomiaceae</i> and the thielavia-like species in the family. <i>Chrysocorona lucknowensis</i> and <i>Brachychaeta variospora</i> are closely related to <i>Acrophialophora</i> and three newly introduced genera containing thielavia-like species; <i>Floropilus chiversii</i> is closely related to the industrially important and thermophilic species <i>Thermothielavioides terrestris</i> (syn. <i>Th. terrestris</i>). This study shows that the thielavia-like morph is a homoplastic form that originates from several separate evolutionary events. Furthermore, our results provide new insights into the taxonomy of <i>Sordariales</i> and the polyphyletic <i>Lasiosphaeriaceae</i>.