Mazosia is one of the most commonly encountered foliicolous genera, regularly present with high species richness in closed rainforest understory communities throughout the tropics. This first comprehensive multi-locus (ITS-nuLSU-mtSSU) phylogenetic analysis indicates a high level of previously unrecognized diversity, with a 50% increase in lineages recognized in this genus. On the basis of combined molecular and phenotypic data, sixteen new species of Mazosia from China are described: Mazosia centrica sp. nov., M. dimorphoverrucosa sp. nov., M. gelatinospora sp. nov., M. intermedia sp. nov., M. papillosa sp. nov., M. pruinata sp. nov., M. pseudoaptrootii sp. nov., M. pseudocorticola sp. nov., M. pseudomelanophthalma sp. nov., M. pseudopapillosa sp. nov., M. pseudopilosa sp. nov., M. pseudopruinata sp. nov., M. pseudotenuissima sp. nov., M. sinensis sp. nov., M. straminea sp. nov., and M. verrucosa sp. nov. A new, world-wide key to the known species of Mazosia is presented. Key words: Diversity, foliicolous lichens, Mazosia, multi-locus phylogeny, new taxa.